I bought a chinese replacement fob for my car, however it required a screw-in key blade rather than the slot in plug that I have, so after melting that one to fit, I decided to replicate the missing buttons for my fob instead - I much preferred the sturdiness of the original key.
Leningrad1's Pug buttons were the correct shape, but the step was too high, and the actual button too low, so using his as a template, I modified both buttons to fit my reconditioned fob.
I chose a higher in-fill because the buttons will be subjected to a LOT of use over time, and the 20% infill ones I first printed felt a little fragile.
I also went for 4 layers top/bottom and sides to ensure a smooth print.
Fitted first time!
20% infill version