Seeking recommendation for indoor walking

I would like to buy a piece of exercise equipment that I can walk with indoors (or similar low impact exercise) but is also small/compact and able to be put away, likely under a bed. My first thought was a treadmill but all the ones that would fit under our bed are out of our price range. I’ve also seen some other stair stepper type machines that look like they might work, but I’ve never used one so I don’t know what to look for. I’d also like to be able to move it to the living room relatively easily (just one room over) as well.

Any suggestions??