I know this is an old thread and I stumbled on it while looking for something else. The alternative I used to replace the key may have been covered already but for what it is worth here is my story.

I discovered shortly after buying my 2002 F-250 that it did not have the key to lower the spare tire. There was only one local dealer that had a full set of keys and they were in the middle of a labour disruption. They told me to contact McGard, the manufacturer of the locks, directly. I called McGard and the people there said to take a small piece of styrofoam from a coffee cup and glue it to a piece of dowel or rod and push it into the tube and up against the lock. This gives you an impression of the lock. I then mailed it to McGard and they sent me a new key. The whole process took about a week and a half before I got the key and that was shipping it across the border to me in Canada as well. Can't remember exactly what the cost was but it was not outrageous.

Of course this does you no good if you are sitting at the side of the road and need to get the spare down in a hurry but it is another source for the key.