Heating pad advice

My lady has endometriosis and she has surgeries yearly to deal, and each time she has a surgery her periods are insanely bad for her… heating pad is dang near the only comfort she gets, but thing is she has it on dang near all day, and we’ve gone through so many heating pads at this point that some times a heating pad only lasts a day and then it starts blinking non stop and didn’t work more than 20 minutes.

Ive be thinking of getting a REBrelief like diaper heating pad thing, but I’m just worried it’ll go out immediately like the others.

Any recommendations or suggestions?

Thank you In advance