This is a PCI slot cover that has a hole to allow a cable to passthrough. The original one only accommodated cables 5mm wide, but I needed to run a thicker cable, so I widened it to 10mm. In my use case, I'm running the cables from a Valve Index directly through a PC case, but you can easily use it for running whatever thicker cables through the back of the machine you'd like.

If you want to change the size of the hole, the original posting has a Fusion 360 file to tinker with.