Well, I don't know for sure but I would start at McMaster Carr (mcmaster.com) and search the rope and wire rope connectors. You might find something there that would work. Might use swivel or union as a search word.

But that is most likely a special item made for that application. I worked as a mechanical designer in a past life and while no expert by any means, I don't ever remember seeing anything like that off the shelf. We probably would have designed it ourselves.