Heating Pad Recommendations?

Hey all! I’m new to this subreddit, but wanted to ask for recommendations on heating pads? I experience period cramps so bad that I can barely get out of bed for the first few days of my period, before it slowly starts dying down. I have endometriosis, dysmenorrhea, and adenomyosis, so the cramps are astronomical.

I also experience lower back pain due to a potential herniated disc, plus my lower back pains gets worse muscularly during my periods as well.

The hotter it gets, the better. The more durable, the better. The longer it lasts, the better.

Does anyone have any recommendations to heating pads, please? I also prefer the texture of the fabric/material be smooth. I struggle a lot day-to-day with physical sensory input, and those scratchy, bumpy, or grooved textures are horrible lol! Thank you!!