I apologize if this has been mentioned, but why not use ab straps as a back band/recliner?
Iron Crush Ab Straps: Home Workout Abdominal Muscles Training/Six Pack Exerciser| Rip-Resistant Nylon, Thick Padded Arm Support & 6.4" Carabiners | Pro Fitness Equipment for Men & Women https://www.amazon.com/dp/B07GFTGKNW/ref=cm_sw_r_
Iron Crush Ab Straps: Home Workout Abdominal Muscles Training/Six Pack Exerciser| Rip-Resistant Nylon, Thick Padded Arm Support & 6.4" Carabiners | Pro Fitness Equipment for Men & Women https://www.amazon.com/dp/B07GFTGKNW/ref=cm_sw_r_