I got mine from Peter Barrats in Stockton, they were £1.50 each, or something like 4 for £3.50. Your problem all going "oh not Peter Barrats", but they all lived very happily, until they decided to commit suicide when I put an internal filter into my tank, and they decided to have a diving competition to see who could jump furthest out of the tank. They are interesting little things, but they can't half jump, so a tight fitting lid is a must. They clean up any leftover bits on the bottom, apart from fish excrement, which only a vaccuum can clean up, they are very interesting to watch, however my mam did not like them at all, but it's only because they had lots of feelers, the same reason she didn't like corys because they have barbels, I mean, who doesn't like corys? They are very hard to find, so you may think they have died or something, but about 2 months after I added mine, I moved them to a different tank and after hours of hunting, I found all four of them. They are constantly on the lookout for food, and it's entertaining to watch them pick up crushed flake and eat it. Great little things and i'd get them for my new cube if I was sure they weren't going to jump out again and my mam liked them, but i'd recommend them to anyone with a tight lid and relatively small, non-aggressive community fish.
Neal