Cord tightener in photos is made from Gator Aid bottle cap. Big enough to use with mittens. Weighs about 1/7 ounce each.
I haven't tested this in the field but it works well on a door knob at home. Probably will never use it. Just wanted to see how easy it was to make. It was easy. Don't know if I have the best spacing on the 3 holes in the bottle cap.