Well I know for sure you can get one from ZZP or Intense. But I also believe you just need part number: 24507524 from a GM dealer. Or you can probably pick it up at a autozone/advanceauto/etc, but I dont know what car its from.
But honestly I dont know if that part number is correct. It is the one listed on the clubgp parts list, but it comes up as a water pump pulley at GMpartsdirect. I may still work, but someone else should know for sure.
Jamie