Looking for non insurance options

My doctor has prescribed Zepbound but my insurance will not cover it even with a prior authorization. I have no pre-existing conditions to be able to get it covered. He put me on it to lose weight to help with my knees. I have 2 bad knees and 1 needs a knee replacement. We are trying to get my mobility better until I am old enough for the knee replacement which is 50ish. Since I am unable to get the insurance to cover what company can I use to get the medicine at a low cost? I have been looking online so far the site Ro seems to be the cheapest.