anyway now that the imperial size won't fit either I'm busy very carefully using a hammer drill and a loosely fitting 4mm hex head bolt that's harder than the screwhead, to attempt to broach it to the next metric size
(yes I did try the "hammer in a torx bit" solution, but not only is it imperial, it's the softest but still magnetic screw I've ever seen. The shards are sticking to my bit via magnet, but torx just further obliterated it. I really need to get a set of like, brass hex bits I guess)
