Thats the problem with the AG. everything is proprietary forcing you to buy their stuff at inflated prices.
$20 for plugs and fertilizer tablets for one crop is expensive. a 3 pack of liquid hydroponic might cost $45, but in that tiny system, it'll last 3-5 years.
visit any online hydrostore and you can buy bulk coir, rockwool, or jiffy pellets (peat moss) you can also buy replacement net pots. buy 2 inch pots and redrill the holes in your AG so they'll fit. then you can use them(the 2" pots) with the medium of your choice.
you can probably get curler sponges at a beauty or hair salon supply store (i.e. Sally's)
Why do you feel it is so critical to use a spongelike material to start your seed in?

Grizzman. Well I thought something like peat moss or this coir stuff,would make everything all messy and full of peat or coir residue...wont it? I mean peat isnt exactly clean thats for sure! And since I dont want the system to clog up, wouldn't peat dissolve and plug up everything? And this coir to? The Rockwool I think dosen't dissolve...but peat will,wont it?. I am trying to find out what these replacement plugs are made out of in that 50 plug pack with fert. And if the company plants in sponge, they must have a reason, that it works good and keeps things clean, I assume? I personally think 50 plugs, with food, for $19 is not to bad of a price. BUT if it were peat moss,or coir,it will dissolve, won't it?? So I figured that this sponge is clean and easy to remove when done. The most you can do is 2 'crops' a year. So how many plugs do you need? 14 is the most you can use. And the tomato kit you can only use 3 per 'crop'! So 50 would last from 3 to 8 years! Depending on what crop I plant. Just all tomatos would be close to 8 years,with that 1 bag,2 crops a year,6 each year, makes close to 8 years on 1 bag. It would probably go bad long before that, or the garden would go bad before that!:)

I have just gotten a second AeroGarden for Christmas,a early gift! And I am expecting a 3rd! So I am going to have a lot of things growing. So the nutrients will be the biggest expense,getting the right ones for seeds that I use on my own, not from the kits.

IF I can just get this sponge material or some other CLEAN material to plant in. BUT since I have all these extra seed kits with the factory sponges and plastic cups,etc... I can plant whatever I want,like my dwarf marigolds and set it for flowers on the front panel,use the flower nutrients and see what happens. Now I have to find the right food for them, for MY seeds that I want to try on my own. Maybe their flower nutrients will work for other flowers, their vegetable nutrients will work for other vegetables,I guess it will be trial and error. But peat moss,especially 'Jiffy Pot pellets',to me sound like they would dissolve long before anything sprouts, wouldn't they? They dissolve on me as it is in that netting as it is! And that is using them the 'standard' sprouting way. And then that would clog everything up! Right?? or am I wrong?

Maybe I should ask if there is a 'general fert'. I could use when I TRY my own seeds and try to get different gardens growing.

The brown thing is a starter plug made from an organic spongelike material available at any hydro shop. The FloraMato is about $12 and will last a long time. 1/4 tsp as a starter solution for the first 2 week cycle then 1/2 tsp for the next and then 1 tsp. until they are done producing.

It's not rocket science and no drills necessary.

those spongelike things look to me like peat pellets. Do they expand when you add water to them?
coir shouldn't dissolve and clog your spayers.
Like I mentioned elsewhere, I use river (or pellet) gravels for a medium. It's easy to screen out the smallest pieces and the bigger ones are too heavy and large to move around if they do fall through the net.
just remember to stick with dwarf varieties of tomato plants. I'm sure the flourescents won't put off enough light for a large plant.
Let us know how things work out.