Get your self a good old-fashioned hot water bottle. I have one with a flannel cover. It helps soooo much when there is a storm coming in, and in the winter time.
I can’t praise this thing enough. Lay it on top of, sit on it, lay on it, hold it on a painful spot. Just adjust the amount of water and it is easier to “form” it the best way to relieve pain and stiffness/soreness.
Its’ hard to balance the feet in a position that’s comfortable, but have had some success heating a towel and rice sock in the micro wave. Put the heated sock so that my heel are resting comfortable covered with a toasty towel and throw the heating pad over that. Works for a while.
Feet aren’t really cold though. It’s either electrolytes or neuropathy, so sometimes the warmth doesn’t really help.