A stock unit will be cheapest- I have even seen them given away free. Chances are you'll want a whole new cat back (cat convert to tail) replacement. For quiet performance, supersprint all the way but it will cost you a bit. Try
www.bmpdesign.com and
www.leatherz.com. The aluminized steel unit does ok by most and you don't have to modify the rear valance to fit a dual pipe tip. Sometimes it hangs a bit off center like my stock one does but can be coerced to hang straight if you insist.
Only 10k miles on that sucker? Is that right? Great find, but does it smell like little old lady inside?