Looks like these are already on sale, and I will get a couple just to get the feeling of the thing. Impressive, especially those on grey, for I really like the colour (sand blasted?).
These are made by or at the order of MS Hobbies of London UK. It would appear that they are milled from a single block of aluminium. No idea where or by whom exactly, but they are sold by the company aforementioned. You can get them from here: https://mshobbies.co.uk/shop/ols/products/grey-aluminium-cassette-for-vef-minox
The grey ones are for Minox Riga, the black ones for other 8×11 cameras. I believe I am going to purchase a grey and a black one, just to get the feeling of it. My main questions would be: 1) do they get stuck in the camera, 2) what size (width) of film they accept (would not be a good thing if they do not fit the exact 9.2mm width), and 3) what about light traps. They do say the felt is provided in the same pack (or separate ?), but I would want to check for myself the how. I get the impression that they may not be needed at all, if the caps do work as they should.
Another important thing would be to see how do the spool caps are secured onto the spool; I cannot see any slots, so probably by friction or tape. Anyways, this news are a good thing for the Minox community !