I keep searching for someone to come out with a bolt on exhaust, but it's not happening.
After some responses I have received (HMF in particular), I have come to the conclusion that there are 2 big factors holding up the aftermarket:
1. The exhaust on the P500 is one piece, from header to tailpipe. The muffler is not removable from the header/midpipe and therefore a "slip-on" system is not possible without cutting the factory exhaust. A full system is considerably more expensive than a slip on. The Pioneer 700 has a separate muffler and header, and there are several slip-on options for that machine.
2. Either there are not as many P500's being sold as other models, or the exhaust manufacturers just don't think so. And apparently they don't believe that the "typical P500 owner" is willing to spend $500 - $700+ for a full exhaust system. I believe that if someone did offer a full system, that is how much it would cost.
I find it strange that Honda designed the exhaust to be one piece, rather than 2 or 3 pieces when many other of their machines have 2 and 3 piece exhausts. However, there must be a reason for it. If it wasn't for that one detail, it would be a very simple adjustment to an exhaust system that they already produce and they could sell it for the P500.