Like I said in the video it was a long search. Cover B is the easiest one to get, followed by cover A.
I kept searching and searching on Facebook marketplace and saw a reply by coincidence that someone got cover C, but was not selling it.
We sent messages back and forth and finally the collector was willing to sell me the copy.
The mediabook is like brand new.
It was strange though to pay someone you don't know (a lot of) money on your own risk, but my knowledge of human nature never lets me down.
The other option is to buy this one at a movie market / convention.