Scan it, make a 3D mold, then CNC or cast from there. From Jay Leno's Garage:

http://widgets.nbc.com/o/47f1317f105123ad/498ebd00a62edaa0/47fe70d4555df05a/9e46bd46/-cpid/ba4377d3bfd6c81

Cool.. I wonder if the do elbow joints.. mine about shot!

That would be pretty handy to have.

Funny... why don't our "offshore" friends do that with genny original parts & sheetmetal?? Then they could repro something that actually fits!