How flexible are you on the outside diameter? Also, how new do they have to be?
If you could handle up to about 7" diameter, I might have the castors you are looking for
I have to see if I still have them, but I know I had, and possibly still have two of the same design as those pictured in the first shot. I can't commit until I see if I still have then.
A year or so back I finally got rid of some large casters I had been sitting on for decades in my ongoing house cleaning efforts. I don't think I got rid of those castors though because they were very high quality. I will caution you though, if I do find them they are very old, likely most of 100YO at this point and they look like it too. The cast iron looks as new, though crudely pinted blue. The centers I think are twins to those in the first picture. No cages, not spinners, just big heavy castors with roughly 1/2" or a wee bit more bonded to the rolling surface.
The heavy use took its toll on the rubber. There are some chunks missing, but not so much as to impact the rolling ability of the castors. I do think they have two bearing races per castor, one per side.
If I still have them, and if you could use 6-7" diameter, then they are yours if I find them. These are exceptionally heavy duty and would easily handle very heavy loads imposed on them. No clue what load limit you need, but these would probably exceed what ever castor I viewed in the thread would handle.
If a guy removed the bearings and ran them through a blaster, aside from tired, but totally usable rubber bonded to the surface they would be beautiful.
I will see if I kept them and can find them. Hopefully the 6-7" diameter is not a deal breaker for you.
I just looked at the pictures again. I saw nothing as heavy as my castors. My castors are not cast aluminum metal, but cast iron. No chance mine are imports. I know mine have to be at least several decades older than my 60+ years of age!
