Just ordered a pair of heated socks. As yet un-tried of course, but currently on offer.
https://www.heated-apparel.co.uk/pro...l-heated-socks Edit.. Don't buy these! See post #31
They come with free rechargeable battery packs on the offer, so I am going to see if one pack will run both socks from a Y-lead and have the battery in my pocket.
I'll let you know.