I use a Cricut infusible ink marker to get a shallow dye-sublimation just from the heat of a diode laser on very low power. I can’t get it as intense as I’d like, as the heat starts to spread and makes the legends blurry, but with appropriate expectations, it works pretty well.

If anybody actually wanted a non-terrible keyboard for a ZX81 emulator, I could do it, but this one is staying an homage. I might add a secret layer to have it output the closest Unicode to the symbols I did include, LOL.