After the adhesive gave her a rash, my mom switched to an old-school method: a heated salt pack. She fills a cloth bag with coarse salt, heats it in a pan, and wraps it against her lower back.
The deep, even heat penetrates muscles and improves circulation in a way topical pain relievers can't match. The salt holds heat longer than a hot water bottle. No risk of overheating like electric pads.
Sometimes the old ways are the best. No fancy packaging, no prescription β just heat, in a bag.