If you have the specs of the drive belt and look for an easy to get alternative you can contact Poly Belts Tech Co., Ltd., they located in Bangkok and are the Thai distributor of Goodyear engineered Falcon SPC belts, which is said to offer up to 33 percent more tensile strength than conventional aramid reinforced belts.
The Goodyear Falcon SPC belts are often used by Buell and Harley-Davidson owners as alternative for the OEM belt.
You can find Poly Belts Tech Co. Ltd at
431-433 Soi Teveevorayard Yukol 2 Road
Telephone: 02-224 3762 (probably only speak Thai language)
Of course the guys at Poly Belts Tech Co. have little idea what belt a Buell Blast 500 is using so you can only call them if you know the specs...