Making one wouldn't be too bad. If get a stack of plate (say 1"), make some circular burnouts how ever big you wanted and weld layers togeather. Is make the layers so there was a cavity inside to revive a heavy dog (think the dog that attaches a forklift mast to the lift chains) and have that turn into a chain. It Woudnt be sperical, would look cylindrical.
I woudnt use CI, way too brittle in my mind.