I wanted a foot switch for something I am working on, so I designed this one. It uses a basic 12x12mm pushbutton. I made 3 versions, that differ only in the size of the 2 screws holding the button mount: 1.6mm, 2mm and 3mm. The top of the pedal and the feet on the bottom are the same for all versions. 

You can wire the button trough the hole on the front. I also put a bit of hot glue on the wires inside to stop them from mowing inside and from being accidentally ripped out. After you are done with the wiring the top part should just click into the bottom part.

I printed the feet with flexible filament and glued them on with superglue.

The feet were printed from fillamentum flexfill 92A and the rest of the parts were printed from PLA (the top from fillamentum PLA extrafill Turkey Egg and the bottom from fillamentum PLA extrafill Vertigo Grey )