Sony Remote RM-SRB5 - an example of simple solutions
This is a tear down of an old Sony RM-SRB5 remote for audio systems. From a design perspective, the following points are interesting: There are 10 mechanical parts in all: top, bottom, battery lid, pcb, metal interconnect for positive and negative terminals, rubber keypad, and four screws. The battery lid is of a design that could be 3D printed provided the orientation of the filament is aligned to create strength if the flexing direction.