You have a few options.
The best is to send your working key out to either Needswings.com or MercedesSwap Shop.com.
The next option is a memnber in the market place in our forum. Look for his add.
The last option is to find a local automotive locksmith as mentioned above, who can clone your chip and make a valet key.
That's what I had done here in New Jersey. The locksmith could not make a working key fob. When I get some spare money I'll send mine out to get another working fob.