Very interesting! I haven’t ever seen an L key with a sleeve like that for screw retention that I can remember! Even searching for it again in more detail doesn’t even bring up anything that looks remotely similar…
Here’s some links for the various sets Fred and I mentioned, with their own methods of screw retention. Some of them are mentioned and articles linked in this ToolGuyd article: http://toolguyd.com/offbeat-hex-key-driver-tools/. I’m curious if you’ve tried any keys using other methods of retention and maybe had issues with them for this application, which leads to the sleeve device you show. Maybe that came like that from a manufacturer of the locks, and it’s something they did special just for them?
Bondhus L keys with ProHold
Wiha L keys with MagicRing
Wera L Keys with Holding Function (only Metric available)
Most of these are available from Amazon or KCTool or similar places. I’d suggest if we can’t find an exact replacement for what you have (I’m still looking because I’m curious about it now), and you need replacements, maybe get a single key in the size you need to try the holding methods on each one, and see which you like best. I did get the Wera metric ones with the holding function, and like them more than I thought originally… I figured all of this holding junk on these was all gimmicks, the 30 year old hex keys I’d been using up til then didn’t have a holding function, and I got by just fine. Other than occasionally putting in a fastener at an odd angle where it lines up just right so the ball gets angled away and thus doesn’t grip the fastener, no complaints. Your application is a little more critical for the holding function obviously, so might warrant one of the others… The Wiha with the ring all the way around might be less prone to potential dropping than either the bondus or the wera when being used at odd angles, though based on your video, I bet any of them would suffice. Difference enough though to be worth trying the options, IMO. I just got Wera because it matches most of my other driving-type devices.