I voted for other. I strongly believe that bettas should be kept in at LEAST 2.5 gallons, 5 being better, and any larger is GREAT. Just think about it, fish were meant to swim. Would you want to spend your entire life in one tiny room?
As for a tank, you can buy one from any petstore, or you could look on craigslist for a used one. A lot of times you can get a bigger tank for much cheaper. Then just clean it with a bleach solution, rinse thoroughly, and you are ready to go (after you cycle it of course).