I doubt you'll be able to make something adhere securely long term. if I was to try I would drill holes on the sides only and fill with hot glue. I added hot glue to keys before and it stayed for a fairly long time. Holes on the top will be annoying on the fingertips. There would always be a perceptible difference. And your filler will eventually fall off. if you really wish to pursue the project you will need to investigate the material your keys are made of and what will adhere to it.

You're basiclaly trying to DIY double shot keys. I think it would be really hard to duplicate this without a factory:

I suggest you go on ali express and buy shine-through key of the same profile and compatible texture. You can buy blank keys or modifier keys in small amounts, even one at a time depending. Make sure to get the correct size per your layout.