Incandescent light bulbs (combined with "light-pipes") has been used for calculator displays [0]. If we're going to even less electronic and more mechanical devices, herkons/relay switches and rotating drums (with engravings) exist. Card-punching devices could probably be an inspiration too.

But all in all, I'd imagine we'd have to settle on scraping the old equipment stocks. I bet there are piles of discarded but still useable CRTs lying around somewhere.

[0] http://www.vintagecalculators.com/html/calculator_displays.h...