Yeh I did a search the pother day and couldnt find anything on this forum reffering to 42mm. And If I had it, I cbf driving to give it.
I have made my own spanners at times, when undoing the gutses of autos
Start off with a plate, measure across the flats of the nut in question, mark out a hexagon then drill holes inside the corners of the hexagon (with a radius that wont foul the nut corners) and then either shear the straight parts away with a cold chisel, in a vice, or jigsaw it with a steel blade.
3-4mm plate can undo most large lock nuts, unless its structural, then you are probably doing something you shouldnt so get the real tools mate lol