Technically, you just need the PCB, short wiring harness and the mounting plate (right?). All the other parts are already there.
Those PCBs came with every F and FC.
Honestly, if you're into DIY, the thing is nothing more than a LED bar. You could buy a simple strip for around $10, crimp the correct connector to it and 3D print some mounting brackets.
I have an unlit L, I might look into this over the weekend.