There are plenty of back therapy devices on the market. Inversion tables could certainly help you address your back issues, but they do take some space. The Teeter Hang Ups P3 happens to be a portable back stretcher that realigns your spine and helps you address back pain. This back stretcher folds up for easy storage. It only weighs 5 lbs. It is made of aircraft-grade aluminum.
This is a device for stretching, relaxing, and decompressing your back. It measures 20 x 11.5 x 3.5 inches. You can get this device for $99.