Treadmill to loose weight

Due to the back injury I'm out of work for 4 months now. Rapidly gaining weight because of the lack of activity and painkillers which stimulates appetite .

Been looking for some second hand models, but they all seem to have same problem - max user weight is no more than 120kg. I'm already 160 and keep putting on more.

Looked at professional ones, but they're way too expensive, I cannot afford them.

Thought I could get some support here.