I was trying to get a valet key recently, and reached the same dead end. No one new about the valet key, despite the picture of one in the owners manual.
I ended up getting a key made by a local locksmith with a laser key cutter. It works great for surfing, etc. but it lacks the transmitter so the car will immobilized if you try and start the car with it.
If you only want a key to get in/out of the car I would go this route as it cost me about $40, vs. $200 for a valet key, if you can find one.
My key:
http://web.mac.com/rick3000/Mods/Key.html