I don't think there were very many of the early ones made/sold originally anyway. The mounting brackets were pretty complex formed heavy gauge pieces but the single bumper tube was only 3/4". The later bumpers were simpler and stronger. The mounting brackets were just two flat tabs you welded to the torsion bar and the bumper tubes were 1".

It gave me the idea that a good way to make a replacement bumper would be to put a piece of close fitting mild tube inside some DOM stainless before its bent.