These are ubiquitous in every kind of consumer and industrial electronics. They are readable in daylight, unobtrusive, and use almost no power. Sparkfun has the Nokia dot-matrix (product 10168) displays but they are rather small, and use comparatively a lot of power (300 uA per the data sheet) compared to segmented displays; and they are from obsolete cell phones so the supply of them must be finite. Plus there are backlit and OLED displays galore.
I’m looking for the plain familiar reflective numeric displays with 0.5" digits or thereabouts, like you’d use in a digital clock, and they seem almost impossible to find.