Here's one on Ebay right now. He says it has a broken tab on the front cover but you can simply glue the front nose piece to the cover. It's basically just for looks and the single tab may hold it fine. Great price & Free shipping too!

02 Mercedes C Class C320 W203 St Wag Engine Cover Intake Air Cleaner 1120940004 | eBay

Edit: If you want to look elsewhere, here's the P/Ns...
Mercedes engine cover #A 112 090 1101
The front part of this two piece cover is part #A112 010 0467