I would think any 8 oz tank would fit in there.  Its a pretty large plane.  Measure the width and length of the tank compartment and compare that to the specs of your favorite brand.  Pack it in there with some foam and maybe a wood spacer or two and go for it.  One thing, Be sure the fuel line (attached to the clunk) is level with the carb.  One problem with the UCD is fuel siphoning because the tank is too high in the stock position.  What I did to fix this was mount the engine upright.