L.A.
I put out my back while pregs. Walking up the slightest incline or the stairs was a super challenge. The belly band helped. I think I got one from the drugstore. It was about 9-12 inches wide, made of elasticy/ breathable material, and had a wide velcro closure. It helped support the belly, and helped support my back.
Some people use them throughout pregnancy to help support their abdominal muscles and allegedly help them recover sooner.
Once my back pain resolved, I stopped using mine.
It cost under $20, and for me proved worthwhile.