ID this fuel tank cap?

[Dana]

This is the fuel tank cap on my new plane. It slips onto the 2 1/4" OD steel neck that's glassed into the tank and clamps there. The black rubber gasket (assuming it is rubber; it's hard as a rock) is spring loaded and presses on the tank neck. I need to replace the gasket (or the entire cap assembly), but I'm afraid to break the existing gasket off as I could attach a new rubber gasket. I'd really prefer to do it right.

So, anybody recognize this cap? Or know where I can find another cap that mounts in the same way? Possibly from a motorcycle, or an auto or boat part?

[Blue Chips]

Pretty close here Dana, could be the same one.
Looked closer, close is all it is

http://www.minispares.com/product/classic/Fuel/Tanks%20fittings/SP228.aspx