There is a black plastic bucket mounted behind the headlamp, that the headlamp mounts to, then there is a chrome (or possibly black) metal retaining ring that holds the headlamp in place and gets screwed to the bucket.
The retaining ring can be bought from several different aftermarket manufacturers, either with or without "guards" in front of the lamp to reduce the chance of impact.
The bucket is more difficult to source. Mopar P/N 55078149AC (Left) and 5578148AC (Right) seem to be the part numbers for the complete headlight assembly (bucket, lamp and bezel). There are people on eBay selling aftermarket assemblies for half the price of the Mopar.
Aftermarket headlamps do not include the bucket or retaining ring.
I'm a JKO Reject