Bought an old Car Seat and weldid it on to the remnants of my old office chair. With a bit of steal tube in the midel, since the hidrolic hight ajustment was to long.
I think it turned out ok. It’s already quite comfortable as it is. The only downside is that you can’t swivel on the spot, as the base is firmly welded in place. It’s not quite finished yet; the armrests are next. I was just too lazy to make them straight away.