http://www.tawvehicle.com/twm_2.htm
TWM gas caps.
AFAIK when I tried to purchase the TWM caps I was told that they don't make them for Hondas, which I find hard to believe. I ended up getting a pair of Vortex caps for my RC31 and MC28. They look almost identical to the TWM "Aluminum "Screw In" Fuel Caps."
http://www.vortexracing.com/index.php?src=directory&view=Products&class0=Fuel%20Cap