FreeTrack LED Mount (3 and 4 Point Versions)

Those are two variants for a Freetrack LED Mount, suited for Headphones with two 5mm Archwires to mount to (in my case, steelseries). i guess you could also glue it just to a other headphone or alter the Baseblates to fit it. It uses 3 or 4 standart Red LED's and a M3 Screw to secure it together. Apart from that you would need 100 Ohm or less Ressistor to power it over the 5V of USB.

I use this tool to figure out the ressistors:
https://www.kitronik.co.uk/blog/led-resistor-value-calculator