The thrift shops around here are chock FULL of the LCD panel monitors at 4:3. That's actually where I bought the one I use with my 486. Might be putting the Enlight on that one and giving the NEC MultiSync 1024X768 LCD to the GEM 286 after I get one of the widescreens with DVI for my current main system. The computer surplus places near me are the same way.
CRTs are a bit different, trying to find them in thrift shops is difficult to impossible, ESPECIALLY the older beige ones from the 90's on back as most of those were scrapped in the 2000's as they all had cable problems, were out of adjustment, had worn out phosphors, and arrays of other things I can fix myself wrong with them (ie stuff that's just focus/voltage adjustments, replacing broken ports and repairing cracked PCBs, and replacing bad cables). The bigger ones are commonplace but might not look so great on vintage systems.
However, some surplus places don't know what they have and that's where I got my NEC MultiSync II that I fixed up, those guys just saw it as an old beige albatross taking up space in their shop, I saw it as an opportunity to have a proper RGB monitor for my Tandy.