I have 3, all mine are midwest, but I'm guessing there are other manfacturers. Deere marketed one, but I'm not sure if they built it.
They may work side by side if identical and plumbed in a manner that they get equal flow. I have a Heil truck hoist that works in that manner.
DO NOT hook them to a tractor made much after, say, 1960. These were designed for 1950s hydraulic pumps, not nwer high pressure stuff. If you do, it may be their last trip up! Hooking the two together, and then hooking to a modern tractor will just blow up both of them.