Just order a bunch of OE filters from BuyMBParts or FastLane. Make sure you specify Hengst, Knecht, or Mann filters (all German OE stuff.) They're usually $5-6 each. Forget any aftermarket stuff from most McParts (Deustch, Bosch, STP, Fram, etc). I buy a bunch at a time, or as part of a larger order, to offset S&H.
Regards,