I think a decent piece of Stainless Steel would be adequate. I like where we're going with this. My father-in-law is a gunsmith. I think I just figured out my Christmas present.A friend of mine made a nut for a Les Paul out of Vanadium--he bought a screwdriver with a square shaft, and ruined some files trying to make it--but he did it.
He loves it--but I don't think he'll ever make a second one.