Once you get the door handle off, you'll see that the lock cylinder is held in from behind with screws. Get a new one (or old one) and have a good locksmith key it for your key.
A GOOD locksmith here has all of the old parts needed to do this and charges me $10 to re-key each one. He has a Chrysler "kit" with pins in it.
A BAD locksmith here once charged me to match a key, but after I looked inside it. He just removed some of the pins and springs.
You can get new matched ignition switches and door locks on Ebay. Sometimes an OLD auto parts store with have a lock set on a shelf and it'll be less than $20.