my lfs will sell bags of hundred for 11 bucks but i have to come get em when they come in. so what i am saying is pay for their order and you should be good?
Why not just set up a tank just for breeding them? Used 55gal's are pretty cheap, and that should be plenty big enough to keep a good sized breeding population.
i get mine from liveaquaria.com 100pk for 29.99 but there shipping for live stock is also 29.99 so its more like 60 bucks. i get them when i get fish cause its 29.99 for your order not each item.
Have you tried asking your LFS to order some in just for you? Thats what I did and I paid $60 for the wholesale bag which turned out to be around 700-900.