In my local 4wd club, we have a member who owns a canvas shop. He has made straps for us real cheap (and repaired the soft tops). He's made them from 3" and 4" strap material.
I'd check you local canvas shop, boat covers, etc. Bring him length & width dimensions, the mounting hardware and just have him sew it together. Takes only 5 minutes.
Suggestion: with the long travel of the suspension, add a hook and loop in the middle of the strap (determine at/near static), so that when you have to lift the tire in the air (place rocks, debri, change the tire, etc) with little lift of vehicle, you can actually lift the tire because you hooked the strap together.