I don't know exactly. I was just clued in that a mate across the pond had picked them up, 50 of them for like 10 pounds sterling which is what around 13- 14 dollars. they looked cool so figured I would ask. You are probably correct that they are custom. It does make it wast to have them inside a chasis.
Look at the wool around the cut line of the circular ABS base. That’s got garage written all over it. Swaging on the lugs looks good, but I have little doubt it’s custom/DIY/small run.