This is a simple device to power a GameCube with a USB-C PD 2.0 supply. 

I will update this with a proper bill of materials/shopping list and guide in the next few days, but for now you basically just need a PD trigger that matches the one in the photos, two jumper leads, and some solder. Hot melt glue or non conductive putty can be used to make the PD trigger a little more secure in the shell.