I use a "cow's knee" commercially made by "Leatherman", but I only use it as a physical protective device to protect the lock when walking in or out of the woods in the dark, so brush doesn't catch on the flint, hammer, frizzen, etc.
When hunting, I just keep the muzzle down, and the lock area up under my coat where it's warm and dry...nothing to have to remove (drop, make noise, make movement, etc) when I want to fire the rifle.
:m2c: