Having done a bit of search, I've not come across a direct replacement.
I'd be tempted to start with a heavy duty corner plate and weld on a short length of iron water pipe.
Maybe getting the parts galvanised for long life.
If you have the old ones and they are broken, a specialist welder would be able to weld cast iron which is what I presume they are made of.
If you are short of the pins, they should be relatively easy to fabricate or get a local blacksmith to help - they are still out there if you look.