Used gym elliptical machine. I bought this from a gym going out of business a while back, but our new place doesn't have room for it. It works, it's self powered when you spin the pedals. Full disclosure though, it is old and the belt is a little worn down, so the resistance only goes to about 80% of its original maximum. It was never an issue for my family, nobody cranks the resistance all the way up anyway, but if you're an athlete or something then you might need to replace the belt to get the best workout on this thing. Elevation still works fine but you have to give it time to charge first.
It is heavy! You either need to bring tools and expertise to dissasemble this thing, or have a truck with a ramp and two strong guys, or if no ramp you need a football team. I have it sitting on a roller dolley right now that makes it a lot easier to move around, you can keep the dolley. I also have a rubber mat to protect your floor from the weight of the machine.