I have a remote battery cable for my P67. But I found out it was easier just to have a spare battery in a warm pocket. Once the cold one in the camera warms back up, it's generally good again. Shirakawa wrote how he would go out with about four batteries per day in his pocket in the Himalayas, and that they were operative again once warmed up even there. He did that entire tremendous project mainly with P67 gear.
But one thing I did learn from serious high altitude mountaineers is to keep the camera gear simple and totally mechanical. The preferred model was some kind of Nikon FM, ideally an FM2n (they never "winterized" them). But for maximum portability I equipped my nephew on his extreme Artic, Karakoram, and Andes expeditions with a basic little Pentax MX - no winterization needed in that case either.