This one
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1,1&item=7631774569&sspagename=STRK%3AMEWA%3AIT
sold on ebay for $20
But I don't see one in any of his current auctions, but you can go to "Seller other auctions" and email him to ask.
There is another seller one (for a track loader and several skidsteers) there selling them for 135 which is 20 less then I paid for a new one from Bobcat.
Here http://cgi.ebay.com/ebaymotors/BOBCAT-A300-S220-S300-T250-T300-MUFFLER_W0QQcmdZViewItemQQcategoryZ46093QQihZ002QQitemZ4637637113QQrdZ1QQsspagenameZWD1V
Ken