A simple 2 parts snap case for a sonoff mini r3 (which should also work for r2 and original mini), which includes a mounting hole for a cherry mx switch to control the relay

The case is designed to completely isolate the smart relay without leaving terminals exposed, so that you can use it inline with an appliance power cord safely. Just remove the relay's original case and put the pcb in the 3d printed case, pop in a cherry mx switch, wire the relay and close everything up.

When printing from the step file you'll need to separate the model in objects and orient the 2 parts independently.