I have one set from a Charger, and know where there's one on a 4D Coronet.
The nice folks from DMT (Detroit Muscle) approached me at Don Garlits, to look at my Charger one.
They said they were thinking about reproducing them.
I think I helped talk them out of doing that one and into doing the 73/74 Satellite/RR one instead.
Rationale was that it's not as noticeable on the Charger if it's missing, and that lots of folks put 71-72 mounts on Chargers, so the bumpers fit closer, which is not really an option on the Plymouth.