The little 35mm metal film canisters would work. There are still some Perfect metal fuel tanks around too. I have made fuel tanks using thin plywood before. I coat the wood inside and out with some epoxy to fuel proof it. Sometimes the fuel tank was the inside of the nose of the airplane too.

You can get a Sullivan gas engine conversion kit for their fuel tanks. It has a different neoprene rubber stopper and some typgon fuel tubing. But for 1/2a you need smaller tubing than what comes with the gas conversion kit. I think you can get the rubber stopper separately too.

Actually those are a pretty good find for those mini Old Spice spray cans. Looks very useable to me.