Ebay and GPR are going to be the cheapest bets. Most of the nicer systems that are cheap on ebay have considerable cosmetic defects and the GPR stuff has yet to really be used, abused, and tested among the community. I'd like to see how that GPR stuff holds up as the exhaust market is dwindling very fast for these bikes.
2001 #62. Ohlins rear/valves, Micron high mount, HyperPro damper, SharkSkinz, Tyga billet triple clamp, Tyga Carbon Fiber fender and hugger, Ti bolt/custom subframe/alien motion 8 cell diet, 15/41 520, COP conv. PCIII, Venhill lines, modified air box, turn signals in headlights...<deep breath> ZG Touring windscreen, Tech G rear sets, CRF450 rear master w/HRC cover, Tokico 6 pots w/V-pads, CRG Bar end mirrors, PSR Shorty levers-use only clutch, wanna-be basic racer paint, Roman Gold PC wheels