I've been thinking about this and don't think it would work well in this application, partly because of the shape of the opening, trying to find a can that would fit in the part that doesn't turn down (bottom tube is not straight across like in a Worksman or Panther frame) and then making the lid hinge so that it has access to the inside. I suppose it is possible, but it would be a hard project, I think. Something that fits the shape of the opening and has flat sides, top & bottom would be best. And it would not have to be as well made as a gas tank since it would not need to be leak proof at the seams. I think you'd be a lot better off going that route.
SB