I made this for the Two Trees Sapphire/Sapphiros Pro/Plus/SP-3/SP-5 but it will mount on any 2020 Aluminum Profile Extrusion.

You will need:

• 2xM3 screw
• 2xM3 20 Series Sliding Drop-in T-nut:
  https://www.aliexpress.com/item/4000149500597.html?spm=a2g0s.9042311.0.0.27424c4dMPf4XQ

The connector needed is a "JST-XH" 3-pin

In configuration.h you'll need to make sure you have this:

#define FILAMENT_RUNOUT_SENSOR

#if ENABLED(FILAMENT_RUNOUT_SENSOR)
#define NUM_RUNOUT_SENSORS 1 // Number of sensors, up to one per extruder. Define a FIL_RUNOUT#_PIN for each.
#define FIL_RUNOUT_STATE LOW // Set to true to invert the logic of the sensor.
#define FIL_RUNOUT_PULLUP