I think most have done sum stupid sh(t as far as window blind piece. I'm sure anything between the barrel and scope would work.
Sorry, but your question was left hanging and I figured I would give you an idea.
I shot with a guy last week that made a strap nearly idetical to that. Goto Joanne fabrics and get a piece of suspender strap 3" shorter than your barrel. Sew one end to run a piece of chain through (as seen in the pic) and then super glue a piece of velcro to the barrel and the other end.
Yes it works for what it's intended for. Match shooting across the course NRA highpower. The barrel heats up during the rapid fire strings and the cloth or plastic band stretched the length of the barrel basically insulate or block the heat form the shooters vision. They are mainly used on bolt action match rifles