Anyone know where I can get a bezel or panel mount socket for single digit segment displays?

 

IEE might still make them. Some of their P/Ns imply a single digit display. Not particularly cheap.. We used them way back when until going to a membrane panel with integrated window. Look for ATLAS and ATLAS 2 Bezel/Filter Display Mounting Systems.
https://ieeinc.com/atlas-led-and-lcd-display-mounting-systems
Old datasheet attached.
Good luck!