I would check in to what bambam suggests. As he also notes, the chrome cover is (pardon the pun) key. If you can get a replacement, then if you trash the existing, it's no big deal.
The lock at the rear of mine was popped out by my ice-chest and I replaced it with a Ford OEM part (~$80.00) that included all the tumbler parts one would ever need. It was easy matching it to the existing key.
Some tidbits here: