I need to source something that will be available in large supply (at least I hope to eventually need large supply).

Interface I'm not sure of yet. I'll work on finding a size that fits the intended design/application first. Monochrome is fine, the application doesn't necessitate color nor the increased cost that would incur. At least not yet. The controller is moot if I can't find something of the right size. And passive is fine.

Something suitable for a phone is about right, as long as I can continue to get it in quantity when I need it. I suppose for proto purposes that may have to do anyway. Not interested in thinking about having one custom-made at this time. I suppose that even the final size doesn't have to be a consideration for a proof of concept prototype anyway.

I did figure that I may as well start thinking about this early on while I work on other hardware, mechanical and software specs. Maybe I should be asking where to get a good wad of startup capital to get the ball going once I've reached the critical stages of documentation...

Bruno