Damascus- can’t imagine that would work. Presumably if it’s 50mm too short he can’t get a stem to clamp on, so the stem like fitting of what you’ve mentioned won’t work either.
I know what you’re talking about (I used to sell them in my old shop) and I wouldn’t recommend them for anything other than gentle pootling/hybrid bikes,
Same with the quill-type adapter mentioned by samunkin.
OP, as someone who has been in similar situations and ended up trying various things/spending a fortune to make it work, I can honestly tell you it’s pointless, and much more hassle than necessary.
Magura forks aren’t mind-blowingly good, so I’d advise getting on the hunt for a different pair rather than sinking a lot of time/money into a bodge.