I was at Costco a few days ago, they seem to have duster sitting out in the open, pack of 4 cans for 14.99. Not sure if thats the stuff you use though (Tetra-whatever-you-call-it)
Current Arsenal: TM AK-47, KSC G19 Heavy Weight, 2 Academy TMP Springers
Owned previously: KJ Vertec M9 Elite, Two no name m9 springers
Current Project Gun: TM M14 OD, awaiting upgrade parts.