In the shul (synagogue) I went to growing up, and in other shuls I've been to, they had a device for displaying the current page number. It was a wall-mounted box with three windows, behind each of which was shown one digit. You could change each digit independently by turning a wheel at the bottom of the device. The device shown in this video has similar functionality.
I am trying to find such devices for sale but so far getting nowhere. Googling turned up this discussion thread from a few years ago where someone else had the same problem.
Where can such a device be procured? What is it called?
The ideal device would:
Display three or four large digits
Allow the numbers to be changed on Shabbat
Be wall-mounted and controlled from below
Operate very quietly, so as not to disrupt prayer in progress
Require as little effort, time, and obtrusion to change as possible (For example, advancing a page should mean something like turning a wheel a little, not taking down the sign, removing one number, sticking in another, and putting he sign back up.)
I'm open to products made for this purpose or creative re-purposing of other products. Perhaps this is a product that's more available in Israel or in Chassidish markets and easier to find if you know good Hebrew or Yiddish search terms.