I have a click heat one that I use for on the go or if I'm doing chores. I boil it and click a metal disc inside to warm it up. It stays warm for up to 5 hours and came with a Velcro wrap.

Peas by cvs. Or thermapearl from Walmart. You heat it in the microwave.

The one I have is called a dr.soooothe they seem to be out of stock on Amazon right now though.

ThermaCare heat wraps come in two different sizes and last for up to 16 hours. You can get them at cvs or walgreens, but they are cheapest at Walmart.

Hi I buy packs of 2 heat patches from homebargins or Poundshops they are really good I do 12 hour shifts at work they have sticky on the back so I just stick them on to my Knickers under my trousers. They last all day so everytime I pop in I pick couple boxes up always keep 1 in my hand bag for when out and about hope you find some