Guessing you have an F or K model with the cap and flip top cover.
Well, gas caps were used across a number of years I would assume. I would suggest finding a bike graveyard and trying a number of caps, not just honda caps. I don't have a dohc, so I haven't tried other caps. If I were looking for 1, this is what I would do.
Shiny or TOOLS might be able to tell you an exact model that would fit.
The ride IS the adventure. The destination is just to get gas!