For tanks for containers for the fry I would check your local dollar store they might have little containers around a gallon or so. If not Aquabid has these AquaBid.com - Your Aquatic Auction Website
They look kinda small, which they are its a quart, but if they use them I guess its ok.
And they fry must stay in the same tank for 2-3 weeks, they are too fragile too move and any changes in water chemistry could kill them. You could either move the betta into a bigger tank to let him build another, try to move the nest into the big tank, or try spawning them into the smaller tank. I remember dmhalfmoon on here said hes bred in a 2g tank so its possible but there is going to be MANY more fatalities especially if its your first time. I would just move him into a the bigger tank and try to move his nest in, even if most of it falls apart he might see some of the remaining bubbles and build on to it.