Merino neck gaiter – This might be the most underrated layering option for cold weather climbing: it prevents heat from escaping your neck, is great for warming numb hands, and is easy to shed while on point.
Portable hangboard – There is no more efficient way to re-warm up for the next redpoint attempt after a long rest. You can buy one you like, or make one with a 2×4” and a campus rung. Hang from it, or use a sling to pull against your own foot.
Rechargeable hand warmer – A game changer for maintaining your hard-earned warm up. Crank it up and keep it handy for those long project belays.