I thought I should share this very simple design that we used in Vallejo. It is a wide mouth bottle, and we used the stronger cap to actually hold everything together instead of rubber bands. Just string and tape were used here. We placed a whole in the cap, tied a knot after passing the string through that we tied off to a clip that directly attaches to the balloon. The two string loops that are seen taped to the camera in the top image get held in place evenly as the bottle cap is tightened down in the bottom picture.