I set up Octoprint on a RaspPi, but the way I ended up building my enclosure meant that the cable needed to go straight down from the top like a filament guide. So using the filament guide as inspiration, here's something that will fit the USB-B male end of a cable.

Drill a hole big enough for the outer circumference (~19.5mm) and pop it in!

(I had already gently hammered it when I remembered I would need a picture for the model. Oops!)