Without knowing what model you have I can't be specific in a suggestion, but I will tell you what I know about the spare on my 2017 2861 model.
Mine came with a spare mounted underneath to the frame just forward of the rear bumper. I know it will be a struggle to get it out if we ever need it, but at least it is there and it is out of the way. Have you checked underneath to see if there is a mounting point for a spare?
2017 Forester 2861DS
towing 2015 Jeep Rubicon