I get mine from a few different lfs
that are near where I live. I am fortunate, I kind of live in fish central, five stores within a few miles, and I go to another city twice a month that has several other fish stores I can get to as well.
As for moulting, I keep a mineral supplement stone in their tank, such as is used for crystal shrimp, as well as a calcium supplement lump for the snails. I have quite hard water, alkaline, which seems to suit them pretty well. No moulting issues so far.