Our local nurseries that have pond plants will not have them for at least another month as our spring has been very cold. They do not have much more than pansies out yet.

I got water hyacinth at a little more than a buck a plant off of ebay. Free shipping.
Here is the link
http://www.ebay.com/itm/121082272724?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649
I am below you in Kentucky and I know I will have to protect mine from frost until about May but am willing to do so.

Impatiens and hosta are at the big box store etc. Watercress (likes running water) is in some produce sections of a nice grocery store. Elephant's ear (not so tiny) is called Taro in the grocery section in a foreign market. Go to the pet store for aquarium plants. Make sure they don't get in local waterways.

I've bought them mail-order at the place below. You do need to learn something about each plant- some are hardy, some aren't, some have special requirements, others will grow too vigorously for the size pond you have. Good luck with your project!

Here is a link that might be useful: William Tricker, Inc Water Garden Specialist

I, too, buy from William Tricker. Sometimes, I can find a decent selection of water plants at local nurseries.

Hi
Texas waterlily has a great selection and best of all great prices gary

Golden creeping jenny can be found in regular nurseries. I've grown caladium in water.

I would try ebay, and also trades on americanponders and on gardenpondforums.

Someone here recommended dragonfly aquatics to me several years ago. I've purchased from them for several years. Plants are always healthy & the customer service is great.

Here is a link that might be useful: Dragonfly Aquatics

Most of mine are from trades or purchased from members on an aquatic and terrestrial plant exchange.

If I purchase commercially they are always from Hughes Water Gardens.

I never see viable plants at big box stores. Always tiny, mislabeled and usually more than half dead.

Here is a link that might be useful: Hughes Water Gardens

try to find a water garden club in your area. My club's meetings feature both free door prize plants donated by members and a plant auction.

At the very least, you'll meet other ponders who might be willing to share.