Prairie Innovations Inc. 1-866-360-6900 in Canada has a tank that mounts under the tin work.. Can not find a web-site but here is a email address [email protected]
Or like the other guy mentioned, a tank from a wrecked truck or something on that order. We used a round tank and got along okay with it.
We used a tank off of a TD 40 tractor. The issue that we have is that the filler vent on the lower tank is not large enough and when you fill the upper TD40 tank you will think everything is full but if you don't wait it eventually makes its way to the lower tank and you wind up with very little fuel. Anyways good luck, and I know the problem, its very embarrassing to run out when you have an extra fuel tank.