Hi, a cheaper option would be just to make and install a small sleeve to fit into the recess, another methos would be to get a recessed nut, drill the centre out of it to allow the brake shaft to fit thru and also file the head flat to allow better contact with the nut, after you have fitted a flanged nut or nut/washer comboe you would not be able to tell the difference. A cheaper option that will have no effect on the braking performance either.........regards wayne davidson Invers NZ........