Anyone recommend a good foot warmer that's cheap to run (and safe)?

[NiteNight]

something like this
www.amazon.co.uk/gp/product/B07LB1H5NC/ref=ppx_yo_dt_b_asin_title_o02_s00?tag=mumsnetforu03-21&ie=UTF8&th=1
which I've only found by googling ... no idea if it's good or not although it was mentioned by @BinkyBoinky a couple of years ago?

ps. I don't really want a heated throw as it's only my feet that get cold

anyone?

My Labrador's tummy works for me! But I would use a wheat bag or two.

A labradors tummy sounds great. I just can't seem to find any on amazon!

Hi op! Honestly, just make your own. Get an old smallish t shirt (kids one should do) sew up all the holes except the the top, then fill with rice and perhaps lavender oil, and sew up the top. Bung in the microwave for about 2 minutes and voila!!

Hot water bottle?

Hot water bottle, rice or cherry stone bag and UGGs boots as slippers! My feet and ankles get really cold and are now toasty warm.

But is a hot water bottle as cheap as an electric foot warmer? I mean the cost of boiling the kettle Vs the cost of electric foot warmer which you can turn on/off easily?