Do you know about Google IMAGE search? If you Google for "flat cable clip" or "ribbon cable clip" and then select "Images" you will see many different photos of similar things. Chances seem excellent that you will see what you are looking for so that you can narrow down your search.
No only am I aware of it, I already did it. All the ones I found were designed to adhesive mount, screw mount or had the cable tie clips. Things designed to route cables inside enclosures etc. Rather than just a free-hanging application like I had in mind where I didn't want anything especially bulky. I figured something small would exist like the actual strain relief on the IDC connectors themselves.
Perhaps what I'm seeking doesn't exist, or maybe the picture I attached, what is being used to prevent the cables splitting is a misuse of something else (ferrite etc).