I got a crapload from Mg and was very happy with them - if you ask around, there are usually even people (like me
) who will send you cuttings for free. Just have to wait til its warmer, and it depends on how picky you are about what you want.

I've bought plants several times from www.aquabotanic.com and been extremely happy. They always arrive in good shape and well packed. There used to be a sticky here with feedback on several online sellers. I guess somebody deleted it. Aquabotanic has been around a long time, and the owner writes articles in magazines. If you go to www.aquaticplantcentral.com you can read reviews.