I'm sorry but, due to the great chaos in the lab, I could not find any suitable example.
The photos are of a production unit, using a PCB with RAFI illuminated tactile switches (they are really expensive).
The panel is milled with a CNC router, but could be replaced by a piece of PCB material.
The holes are square to accommodate the switches, that are rather large, but could be round if the switches are smaller.
The membrane is actually silk screened polyester, but we built the prototypes using a good transparency film, for use with overhead projectors printed by a standard office Canon ink jet printer.
Dual side adhesive film is available from hobby shops or arts supply shops. Buy the best available, press it very well in place using some tools to apply force (a small spoon is suitable, if you do not have other available) and leave it sitting for some hours before applying pressure on it (these are "trade secrets" that a supplier taught me years ago: the adhesive surface is formed by small spheres of adhesive, that mus be broken by applying high punctual pressure, and the adhesive must "cure"for some time)
The dual adhesive film is cut with a CNC router, but for the prototype we glued it to the panel, cut the holes with a standard blade cutter, then take away the outer protective paper and glued the printed film.
The printed film has the habit of being cut by the hedges of the panel's holes, so it is a good idea to chamfer the hedges using a big de-burring bit, or with a small file and a lot of patience).
Best regards