This is a stepper motor directorial indicator rotation visualizer for the bontech extruder. The stepper motor brand is OSM which has a smaller hole in the motor than the LDO motors used by Prusa.
I sourced 7 mm by 3 mm magnets from Amazon. They actually measured 7 mm x 2.72 mm so I had to stack two together to get enough clearance otherwise it would rub on the motor housing and not turn.
The link to the magnets: https://www.amazon.com/gp/product/B076Q77T7W/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1