I wanted to rack mount my DVI switcher but the wires had to pass through a wall and none of the furniture grommets I had were large enough to allow the connector to pass so I designed my own. This will print all parts as one piece that you will snap apart when done. The flat washer goes behind the nut to protect the surface from the twisting of the nut. The insert was designed to block the hole from the wires falling back through, they fit my wires but might be too large or small for yours, check first.
You may need to clear out the slot that retains the insert. I used a small file and it worked well.
I built tabs to connect all the pieces so the part prints as one unit. This may or may not work with your setup.