Garage gym cardio equipment for fucked up knees?

So just finished up most of my weights for my garage gym now I have to think about cardio, problem is my wife who I am sharing the gym with has really fucked up knees, so running/treadmill is out of the question.

Because of this we're considering an elliptical or stationary bike (though she prefers an elliptical) and I'm just having a hard time finding good recommendations on either of those, but also wanted to see if anyone else had some other recommendations. We were considering just getting bicycles, but there is snow/ice on the ground here 5 months out of the year, so it would be easier to just get something that works year round for now lol

I'd like to not spend too much more then $1000, the cheaper the better but can spend more if it would make a world of difference. Thanks in advance.