Most shops know a BG distibutor and many I know like this product:

BG Frigi-CleanŽ
Odors, bacteria, mold, spores, fungi, road grime, nicotine oils and debris accumulate in your car’s air conditioning evaporator. BG Frigi-CleanŽ restores heating/cooling efficiency and freshens interior air. It is a unique cleaning solution designed to quickly and effectively remove foul odors, bacteria, mold, spores, fungi, road grime, nicotine oils and debris that accumulate in your car’s air conditioning evaporator. BG Frigi-CleanŽ is injected directly into the evaporator case. It foams up to completely fill the evaporator core where it also blasts away bug parts, pet hair, nicotine residue and other garbage. BG Frigi-CleanŽ is biodegradable, non-toxic, non-corrosive.Part No. 709 Net Wt. 7 oz. (198.4 g)
Volume 6.65 fl. oz. (197 mL)