You can also get a flat master key. I got all three keys with my car and I thought the flat key was the most ingenious thing I had ever seen. It goes right in your wallet and you never know it is there. Its great if you forget your key ring somewhere, you always have a key in your wallet. Like Larry said, your dealer can order any keys for you if you give them your VIN.
1995 E420 - retired
1986 420SEL - retired