So darling of you! I use my hot water/ice bags sooo often—these are the set I have:

Elitehood Ice Cold Pack Reusable Ice Bags Hot Water Bag for Injuries, Hot & Cold Therapy and Pain Relief with Elastic Breathable Support Wrap, 4-Pack, 3 Sizes (6"/9"/11"), (for Hot Therapy is 50-60℃) https://www.amazon.com/Elitehood-Reusable-Injuries-Therapy-Breathable/dp/B074TBDS6S