I have personally bought the finger condoms (a.k.a. finger cots), at the drug store. And they do work. The problem with them is they are kind of thin and if you try to stretch them too far or go over a large front site they can tear.
Also be sure and remove the finger cots or what ever you use over the muzzle, at the end of the day. They can cause rusting under them. Especially if your rifle went through some bad weather.
If I leave a rifle loaded, I normally tie a red bandanna through the trigger guard. I tell everyone in the house, that a red bandanna in the trigger guard means the rifle is loaded, and besides, they have no business touching my guns. Loaded or unloaded. I had a little incident with a curious nephew one time (it was unloaded) and had to straighten him out a little.