Looking for some kind of versatile hot-shoe mount that would be strong enough for a smal light (like 123 mini). This would be used for nighttime video recording and for focus assist.
Surely. I found this product at the shop of a german photo warehouse (a german equivalent of B&H ). And Fotonovum, the maker of this clamp, is a small company which seems to have bolted together a flash (strobe) foot and a Mic holder.
So if you're into DIY, look at a shop for musician's equipment, or take a bulldog clip at your local home-improvement market. Flash (strobe) foot accessories should be available at a photo warehouse, for example here, there or this item.