You're right that they won't breed. They need saltwater to breed. From what I understand, they are saltwater snails that can be converted to freshwater, and since that process adds extra effort on the part of a breeder/store, they're a little less commonly sold as freshwater snails. I had some that I'd picked up from my LFS back in the day, but I haven't seen them in a store since. Have you tried aquabid? I don't know if any of the sellers are in Canada, though. Once you look at a few pics online, though, you should be able to tell which ones are Nerites for sure. I can't think of any other freshwater snail that's about the same size and patterning, so you should be able to ID them.