Here's a bunch on car-part.com for $50:

2000
Air Flow Meter
Mercedes C Class 202 Type, C230 A M20412 $50 Millis Used Auto Parts USA-MA(Millis) Request_Quote 1-800-287-4110 / 1-508-376-9680 Request_Insurance_Quote

1999
Air Flow Meter
Mercedes C Class 13050 $50 Roadway Auto USA-NY(Oneonta) Request_Quote 1-800-562-0014 / 607-432-0014 Request_Insurance_Quote

1998
Air Flow Meter
Mercedes SLK 230 AIR FLOW METER,6 MONTH WARRANTY A AS3793 $50 Alliance Auto Parts USA-NY(Woodside) Request_Quote 1-800-323-4500 Request_Insurance_Quote

1999
Air Flow Meter
Mercedes SLK 230 2.3L,AIR FLOW METER,6 MONTH WARR. A AS4730 $50 Alliance Auto Parts USA-NY(Woodside) Request_Quote 1-800-323-4500 Request_Insurance_Quote