I think maybe those tanks are a bit small. Betta's need a heated, filtered tank and a tank that size is a bit small to be kept heated. I think the I read somwhere that the smallest size tank that you can safly keep heated would be a 2.5 gallon. :-\ Betta's can "live" in a 2.5 gallon but will do best in at least a 5 gallon tank.
I live in Canada so US prices are not like ares. I do though live nead a walmart but have found that they do not have that great of stock. The boxis are always open and stuf is missing.... Any thing elce?
You might try looking for one of these and Walmart here has the Marineland Eclipse Hex 5 for $29.95 for the whole kit without the heater. Anyway there are these that would work very nicely for a betta and a couple small friends.
This one is the one that is $29.95 at Walmart:
There are also other shopping places to look online if you want to browse.