Son....you better be damn sure what you have there before you go belt shopping. Kona spot-on as usual with his info above which is always outstanding. IF your 2003 S model is now sporting a rear 65T pulley/front 27T pulley......AND your old belt is 1-1/8th inches in width....then you'll need a standard 2004 and later S model stock belt which is 128T count. here's your factory part numbers:
G0500.1AAH (suffix U8A) which supersedes all previous part numbers G0500.1AAA, G0500.1AAE, G0500.1AAG
dealer list price is $186
Goodyear----BDL---Panther also offer alternatives. pitch is 14mm.