Shoulder buttons for GameBoy Zero. This battery cover /shoulder button combo works without modifying the GameBoy rear shell.
This is a work in progress.
For the buttons, I soldered tactile switches to a perf board. You can use screws or glue gun to secure the pcb. The screws used in my build are the same size screws that come with the original gameboy.
Check version 2 for a better/more easier to print design: