A simple cord manager. Slip the cord into the slot and feed as much as you want into it. It should accommodate wires and cables up to 6mm in diameter. A fair amount of cord should be able to be fed in.
Print the two sides with the case split on top and it should print well. There are little 3mm pins but I guess 3mm filament would work too. Push it together with the pins and add glue if you want it extra secure.