I agree with the guys above about getting into the trunk from the inside but if you want to save the lock cylinder I would drive down to a lock smith and he should be able to make you a key in just a few minutes. Good luck.
You might check with AMD (all metal direct I think) and Good Mark industries. They are making more and more sheet metal parts all the time. I know they make roof skins for cudas but not sure on challengers. Roof skins for cudas are I think between 500-600 dollars. The shop I use has used several...