While I wait for larger protoboard to arrive I decided to try stuffing an Arduboy into that old Pac-Man handheld I found. I was able to solder the button BUS to a 4x6 protoboard and added headers for the screen. Unfortunately, the issues with the dpad persist, down is hard to trigger. It’s easier if you remove the cap but the switch is hard plastic that’s uncomfortable. I think I can superglue one of my other button caps on it, though.
I should be able to cram a pro micro in there it will just require a lot of cutting and soldering wires. That’s not really a time investment I want to make right now, but I’ll keep thinking about it. I can easily run the OLED GND and VCC lines down the protoboard. I’d also need to desolder one of the pro micros although I’m pretty sure I can pull the plastic header part off and bend the pins horizontal and not have to actually desolder it.
When I bought the Pac-Man they also had an Atari Centipede Electronic Carabiner, but I think if I tried another retrofit I’d choose something (much) larger.