They can be difficult to come by. Currently Park Seed has them (Egyption Walking Onion). I have done business with them in the past and they are OK.

Here is a link that might be useful: park seed link

Do you mean green onions that split during the growing season and produce more green onions? (Some shallots, Evergreen, some fistulosum)
Or do you mean bulbing onions that produce many onions after leaving dormancy? (Potato)
Or do you mean top setting onions that produce onions on bloom stalks? (Egyptian, top-set, walking)
Or do you mean green onions that produce many onions just after leaving dormancy? (Shallots)

I mean green onions that split during the growing season & produce more green onions. anybody know where to get them??

I have been searching for the same plant that you are looking for. In horticulture the term is bunching. I agriculture the term bunching means it will grow close together. Because of this you cannot trust what the seed companies say. I now have 72 varieties of alliums. The result of my looking for "bunching onions." So far I have 14 edible alliums that will devide during the growing season. Some of them such as the Egyptian, Top-Setting Japanese and Potato Onions divide rarely if at all. My arbitrary cut-off line for what I would call a "Dividing Onion" is eight onions from one. That means four divisions a year. I have one that I would estimate will do six divisions a year. My best five are all unnamed. Starting this fall, I will take samples of the most productive and try to get a better measure of productivity. Here is my list in order of favor.
1. Ultra Tough, the only way I know to kill it is to eat it. Between dormant and active production one will give you 20 at the end of the year.
2. Onion Mass Producing Japanese I am guessing that one onion cared for will give 64 or so by the end of the year.
3. Ultra Productive Shallot, makes four or so a year and then mass produces from dormancy.
4. S1 Productive Redskin Shallot, This one is doing so well it may be moving up my list of favorites .
5. Garlic Chives, Easy to find, worth growing.
6. Chives, Easiest to find, a must have.
7. Iitoi's Onion, available from www.nativeseeds.org
8. Small Welsh Onion
The following will divide but are not as quick to do so.
Society Garlic, Potato Onion, Egyptian Onion, Mirage Shallot, Matador Shallot

I am still looking for several alliums,
Perlwetzel
Beltsville Bunching
Texas Natve Bear Garlic
And the most important, Perpetual or Multiplying Leek. http://www.ginnysherbs.com/heirloomflowers.html has it but won't ship out of NZ. It used to be popular in my area. Now I cannot find it.

I am new at gardening. I bought some onions that are called mulitplying onions. They are growing "onions" at the top of the stalks. Is that normal?

I grew multiplier a/k/a potato onions last year with great success. Mine came from Territorial.

Hello..I also bought some multiplying onions and they are doing great in the garden..They have what looks like a seed pod on top..I have never had these before or even gardened alone before so do not know what to do with them next..Do I just leave them in the garden,,or pick the seed pods and plant them...please..Any information will help..Thank you...oharamom7@aol.com

I'm growing I'itoi's Onions from nativeseeds.org. This is my second year growing them, and they do great. They just divide and divide into big bunches of green onions until summer when they dry up and go dormant. Then I dug them up, traded out some of the bulbs, replanted the rest in fall, and off they went again. Nice flavor, too.

I was given some Potato Onions this year and they are growing like gangbusters. With a little luck I should have plenty to plant in the Fall.

I have some of neohippies i'itois and they grow gangbusters for me too.

I also have a 'red blush' bunching onion from garden center seed packet, it produced bunching onions that split many times per year.

I have evergreen hardy white too, they are HUGE >1" diameter, but they only multiply about 4x in a year (though you can let them flower and go to seed to get a lawn of them).

I believe I have the onion you are looking for! I purchased the last 14 at a nursery. My grandpa took me there as a boy and I asked them what ever happened to the multiplying/bunching onions they used to carry. A man working there said they had some on the back. The original gentlemen that grew them in the area had passed a way. In 1 years time with little effort 14 turned in 320! They grew all through the summer and winter. Even the once in every 10 year snows storm we had didn't even make them wilt. 1 onion can easily turn into 20 fast. They look and taste exactly like the table onion you'd buy at HEB.

I'm also looking for a multiply/bunching onion. Would anyone be willing to sell some ? Went to a website mention in one of the post and they are sold out,just my luck!Thanks!

Try googling 'hardy bunching onions'.

The first four nurseries to come up, Johnny's, Southern Exposure, HighMowing, Stokes, are pretty dependable and honest sources. The most common variety they all seem to off is Evergreen Long White. Most everybody seems to have the seed. You can even get plants from Burpee.

A lot depends on how far north you are, some varieties are fabulous like the litoi but not hardy enough for most of the north. Also you can harvest green bunching onions off any of the multipliers, you just do it before they bulb up. There are a couple of ways you can go, but the Evergreen Long White is probably the most widely available.

Probably the best commercial source for bunching onions from seed is Evergreen Seeds , they carry 9 varieties. My experience has been that the larger-stalked varieties (such as "Fuyuyo") tend to be less winter hardy, and multiply more slowly. The larger ones can reach close to 1" in diameter, and are best suited for milder climates... but while they can be grown as perennials, I note that quality deteriorates after the first year, unless they are moved or you let them reseed in place. Those with smaller stalks (such as "4 Seasons") are more winter hardy, and multiply quickly. In a 9-variety trial several years ago, 4 Seasons split at least 10-1 the following year, and quickly formed clumps.

There are quite a few heirlooms (some topsetting/walking onions, some bunching) that will also multiply quickly. The bunching onions "Franz" and "Stevenson" have 1/2" stalks, are very winter hardy, and multiply quickly to form clumps... the best combinations of size, multiplication, and hardiness that I have seen. I will have seed for one of them in late summer... but the record was lost, so I don't know which of the two I'm still growing. :-(

"Egyptian" and "Catawissa" are the standards for walking onions,
exceptionally hardy, and forming large scallions in Spring & again
in late Fall. You can't go wrong with those, they thrive on neglect, and a clump will last for years without care... and even spread, if you don't remove the top set bulbils. The top sets are occasionally offered commercially in the Fall, but the best source is another gardener, since both onions are widely grown.

"Grandpa Achors" (a small topset onion) multiplies nearly as fast as chives (and is just larger), quickly forms large clumps, and will form small white onions if divided. "McCullar's" (another white topset) is larger (close to the size of supermarket scallions), multiplies 4-5 times from the base, and will form nice 1" white onions if divided & given space. Both are very winter hardy, and form topset bulbils in late summer.

https://www.kitazawaseed.com/ is very similar to Evergreen with a similar broad Oriental selection including a similar selection of bunching onions and a very large selection of Oriential radishes among quite a few other offerings.

An elderly oriental lady gave me a few small white onion bulbs that when planted would turn into five to ten onions. Never had any go go seed and after a few years I lost them after stopping gardening for a couple years. Can't find them anywhere. I don't even know what they are called. Any help would be greatly appreciated! these bulbs were small and not round.

Try white potato onions, or white multipliers. Google white potato onions.

Try http://www.southernexposure.com/white-multiplier-onion-plants-p-2118.html

Shipping will probably be in the fall this year.

This guy has perennial leeks:

millbergfarm@austin.rr.com