I made a two-button footswitch for changing Helix patches up and down, using a generic (Elegoo) Arduino Nano board. It sends MIDI program change messages, and is endlessly customizable.
Complete parts list:
Hammond 1590a enclosure
Elegoo nano (set of three for cheap https://www.amazon.com/Arduino-Elegoo-ATmega328P-without-compatible/dp/B0713XK923 )
two SPST momentary (normally open) switches
LED and 220 ohm resistor (optional)
panel-mount MIDI jack
I built a new program switcher into a plywood base for my Line 6 50 receiver and an expression pedal, for ease of portability and setup.
Let me know if you would like to buy the MIDI pedal I built, shown above, the one in the Hammond 1950a chassis.