RE: revolver sling?
I think the poster above is talking about the "trigger sticks". I couldn't find the one with the boot loop, but the rest of the description sounds like them.
Also, I seen on another forum where a guy used a simple piece of parachute cord with loops on each end. He puts each thumb in the loops and wraps the cord around the back of his neck. Just get the piece of cord the right lenght and it will pull up tight giving you a steady hold on your hand cannon.
Hope this helps.