Do a search for PATS keys. If you have two programed keys, you can program a third, up to a total of 8. If all you have is one then you must go to the dealer or a special locksmith for the second.
From a post on March 1;
From the Articles/Specs available at the top of the forum;
PATS Key System Programming .: Articles
I buy key blanks from a supplier on E-bay. I have 4 keys to each of my 4 vehicles. 1 for me, 1 for the wife, 1 in the house and 1 with the father-in-law so that he can bring it to me should the need arise. Even if I lose a key I still have 2 at hand so that I can program another. I also have 2 spare blanks in the house for the future should the need arise.
The price for getting all of them ($100 for 10 blanks) is less than what it would cost for a trip to the dealer for the first lost key.