I recently took a different approach to cocked and locked safety.
When I first got my Kimber 1911, using the original extended left side only safety, I had the safety wipe off while carrying the gun in a fanny pack with a built-in holster with a thumb-break safety strap set up to pass between the hammer and firing pin. Later, after installing an ambi safety, I had the safety wipe off while carrying the gun in one of the best IWB holsters I have seen.
So, I had Matt Del Fatti make an IWB holster with an upwardly extending tab on the inside of the holster. Picture a sweat guard but one that doesn't extend up all the way. The tab includes a thin metal reinforcement covered by a thin piece of leather, in much the same manner as a reinforced IWB top, but the reinforcement is for the tab only and the mouth is otherwise unreinforced. The tab extends up under the left side safety lever, making it impossible for anything hitting the right side safety lever to wipe off the safety with the gun in the holster.
I can now carry a 1911 without occasionally looking for opportunities to check my safety's position when no one can see what I am doing.