I found the ES Composites one here: http://www.escomposites.com/petrol.htm

Now for a header...

Hatori do a nice header for the OS 160---part no 907---and it just needs new (closer together) bolt holes drilling for it to fit the MV--oh and a bit taking off the top of the mounting flange to miss the MV's head fins---I've utilised it for the MV160 glow.
I'd guess Ed Skorepa (ES Composites) would be your man in N. America for a light Composite pipe for a petrol 160.

Thanks - that looks like the ticket