I do not recall the official name of these things, but back in the late 70s and early 80s, you used to be able to order little metal retainers to slot into the cable guides on the back of the ][ and ][+--as those systems have four open slots for them, not a series of DSub pop-out panels--into which you would mount DSub connectors at the end of ribbon cables. The Apple Serial cards always came with one that was for DB-25.
They also made one to keep the Disk ][ cables from slipping.
Do any of you know the official part decription/name for these retainers, and do you have any spares?
I could see making them in plastic with a 3D printer these days, but I am not set up for that.