This is my rendition of some LED lights for my MK2S. They work fine with the spool holder either factory or the one shown in the photos. Make pretty good light for a small foot print. I used these LED's (below) and I used an old 12v router power supply for the lights. For the switch I used a small RC hobby slide switch and printed a small box with each end being for the box receiver so I can disassemble as needed.
I attached the light switch box to the top of the power supply with some double sided 3M adhesive- did not want it to be permanently mounted.
I used the basic mount from the spool holder to make the holder for the lights. Awesome spool holder unless you opt for the shelf mounted as I did.
My Spool: https://www.thingiverse.com/thing:2448862
PLA+: http://amzn.to/2w85Ec5 (good filament for many projects)
3M: http://amzn.to/2vBKeT9 (same glue as used for the PEI sheets)