Here it is. my personal shift light/ button box ive been using for years. could definitely use some upgrades but this was my first make of it, it fit well enough so i stuck with it. secured to the wheel with 3 zipties. Simple, Effective. Easy.

Print at 0.2mm layer height so they led can shine through the plastic properly.

items used:

1x arduino pro micro

1x MAX7219 8x8 LED Matrix

6x Slim push buttons

1x usb cable

Also slots inside for rgb strip to be used as shift light. all programmed through SimHub. wiring is routed through the internals of the wheel. if you cut the end off a usb cord there is just enough room to push it down the shaft of the wheel, drill a small hole in the back and now your shift light / button box is attached with zero wires to get in the way or tangled. just one wire running out the rear with the other wires.