Custom LCD segment displays can be produced via a contract manufacturer:
Granted, I doubt that needs to be done here. I can imagine AMC used whatever was inexpensive and plentiful to get a hold of when they had the clocks produced.
I have not yet had the time to look at and analyze the broken clocks I got from you, but whenever I do, I'll let you know
Best case scenario, a similar sized transflective 7-segment tft LCD can be found and utilized.