Found one for you:
http://phoenix.craigslist.org/evl/mpo/4915402751.html
CR500AF FMF Pipe - $200 (chandler az) This is an FMF gnarly pipe made specifically by FMF for the 2005 era CRF aluminum frame chassis CR500AF bikes. It can be modified to fit a stock CR 500. Excellent condition no dents ...