Producing one's own calculator keys?

[Jeff_Birt]

One could use the laminated used in sign making for the key tops. This has a thin top layer that you V carve through to reveal the layer of plastic underneath. The cap would have to then be inset into a key body. All together a lot of work.

Filling like blackjetrock did is probably the most workable idea. Even if the filling is messy, you can sand or mill the top of the key to reveal a nice even surface. A resin printer would work well for keys.