I know this is not exactly answering your question. In the "for what its worth category", similar fixtures are available at Camping World. (However, they are not quite the same as our FR units.).
I've wanted to mod my fixtures with a compatible 3 position switch.
I want to set up -- "single light on", "both on", and "all off" functions on my fixtures. Switch "cosmetic matches" have been the sticking point.