Does anyone know of a source of images for key caps? I would like to upgrade my keyboard simulator to look more realistic. Right now it is just text buttons.

Do you mean photos of keyboards? As there's a whole world of keyboard collectors, I expect high resolution photos should be fairly easy to find.

For example a Model F
https://i.redd.it/h7k70tgdlz331.jpg

But now I look, I see that there's inevitably some perspective effect - maybe that's not enough?