First port of call:

mercedes smog pump items - Get great deals on eBay Motors items on eBay.com!

I found one advertised as new for $200! - But i think it was reconditioned, either way it works now and it got rid of the CEL!

EDIT - check this one out http://cgi.ebay.com/ebaymotors/Merce...Q5fAccessories

Regards

AR