Wool fingerless gloves, wool gloves, wool trigger finger mittens, wool glomitts. Helps if they have something like a deerskin palm patch to give better grip on rifle.
If you want to spend a lot, the Buffalo Wool Company will sell you versions made with buffalo hair/fur/wool (whatever it is that bison wear). thebuffalowoolco.com
Other stuff can work when it's dry or dry/cold, but throw in wet and wool still rules.
