I've seen those little triangular betta "tanks" for sale. I personally think that bettas need a little more swimming room. I have one of my females in a 5 gallon (my other bettas are in a 28 gallon), and she is always swimming all over the tank. I'm not saying you have to go out and buy some elaborate tank setup, but 2.5 gallons is usually considered the minimum for bettas. Plus, a slighty bigger tank means less maintanance, and allows the tank to cycle. Keeping bettas is little bowls for their entire lives is like keeping a cat locked in a cage for it's life... a cat could live in a cage, but it wouldn't be happy, or as healthy as it could be.
Two and a half gallon tanks are less than ten dollars at any pet store. Walmart sells a 5 gallon Eclipse with built in light and filter for $28. It's a nice system, and it'll last forever. I know you don't want to buy a new tank right now, but it might be a good investment later on. :D
I agree about the snail, they produce tons of waste. You'd have to do more water changes with a snail.