I got mine from PetSmart for $2. ^.^ They're called mystery snails. ::) Because when they first showed up in pet stores they didn't know what kind they were but they're a part of the apple snail family. :)
MOST bettas get along with snails, African dwarf frogs, and snails. Peach doesn't get along with the shrimp. :P He thinks they're snacks. :P And I think he may be too aggressive for a frog.