ARB USED to sell a rear bumper in the USA but I believe it is NLA here. It was similar to the Kaymar in design but not quite as stout. The ARB rear bumper didn't fair too well in the rocks; the side wings were not made strong enough to resist bending. With a little reinforcement it would have been fine though.
I have one of the few ARB rear bumpers that I have seen. It was discontinued a while back. I don't know the dates of production as I purchased it used. Mine seems as though it could take a loooooot of beating.
However, it does stick out a bit far if you don't cut the rear crossmember that goes from each side of the frame. I did not do this as I wanted to keep the frame stock.
I have a picture of it in Cruiser Garage. However, Cruiser Garage does not seem to be working for me lately and I have a silver star???
I will post a pic when I get to the house.
Long story short, you can't purchase them unless you get lucky