There were only 128,539 Demons made if the production numbers are to be believed. There’s probably less than half that many still around. Now, with their popularity and the availability of reproduction Demon tail light panels it is a little surprising there aren’t reproductions. But there aren’t reproductions for a bunch of the A-body years/body styles, or even some of the E-body styles.
Now, why you can get reproductions for a ‘71 Satellite and not other models I’m not sure, seeing as how that was a 1 year only tail light and not a super popular car. Not much rhyme or reason to it.