Good luck trying to find one. I've been waiting for years for a decent one to come out.
Sounds like a lot of effort .... why not just buy a Happ Super Top Fire Button and put time/effort into something else?
In my case, I just do not like the Happs, they are about as ugly as can be, and not very comfortable. They just do not go with the way my cabinet looks. I would like top fires to look like most of the normal joysticks that come out, kinda like the old wico ball tops and bat sticks that I use to have back in my commodore 64 days.
Allister Fiend
(Still hoping after all these years that Andy or Randy comes up with something.)