OK, I got the latest and greatest:
Both FMF and PC DO make pipes for the CR500AF, as I said. However, ProCircuit only sells the 500AF pipes to Service Honda. I assume the 500AF silencers are in the same boat. FMF will sell the pipe and silencers to anyone, but they only make a "Gnarly" pipe for the 500. The "Gnarly" model, if you don't know already, is more of a low-end design.
Kiwibird, are you interested in selling that ProCircuit pipe? Or perhaps helping me procure a new one from Service Honda, assuming your 500AF is a "genuine article" of course.
I'd rather not go the "buzz off the center mount" route as I'd like a nickel-plated pipe for corrosion resistance.