I have an old Stagg case that I used to keep a some guitar stuff in.

Its ideal for this build; the hinges separate, meaning I can build my project into the lid and just remove the rest of the case for use.

This pic shows the Pi and interface in there, with an Arduino Pro Micro breadboard set up to test a 5 button, 2 potentiometer midi interface.

Once I've got a script that will work with the software I'll build a footswitch into the case.

The Pi and Arduino will be inside the footswitch, and the interface with be countersunk into the top of the angled switch. The space on the right of the picture will be where I build an expression pedal.