An alternative would be something like a bag of rice or cherry stones. You can microwave them and they won't feel cold when they lose their heat. (See also htt

An alternative would be something like a bag of rice or cherry stones. You can microwave them and they won't feel cold when they lose their heat. (See also https://news.ycombinator.com/item?id=30025026 https://news.ycombinator.com/item?id=30025026)