Maybe it's because I am British but hot water bottles have been something I've owned and used forever. They just exist as a thing you use. To warm the bed, or your feet, or your back. Given that the British also have electric kettles for warming water they are simple to use.
I did try to buy one here in Portugal and I was sent to the pharmacy where they had a tiny little one that you might use for pain relief.
I did try to buy one here in Portugal and I was sent to the pharmacy where they had a tiny little one that you might use for pain relief.