O.B.A. for 99-present GMC 4.8 v8

Where would a man find him self an On Board Air kit for a 99-present GMC Truck with the 4.8 v8. I have found some for the 6.0 Vortec but none for my truck. Really all I need is the brackets and pullely but if have to Ill buy a whole kit. Any help on finding this would be much appreciated.
Thanks,