There have been "universal" Mugen knockoffs on eBay, but I wouldn't trust them... Now HyTech Exhaust is making their own 2.5" twin-loop muffler. For those that don't know, HyTech is serious racing exhaust type stuff...well known in the racing world...
Anyway, I thought this might be cool for a custom single exit exhaust on the NC. I wish I could weld, or I'd try it myself!
Their website sucks, so you have to go to the main page and click on "Muffler".
http://www.hytechexhaust.com/