About 7 feet of 3/8 inch latex tubing (found in the plumbing section at Lowe's...$1.82/foot...they have to cut it for you), and fabric to sew.
Sew a tube about 9 or 10 inches long, and 8 inches wide. And make another tube for the handle, about 7 or 8 inches long (you can adjust these measurements)
Next, sew about 2 inches in from each side, allowing the tubing to slide easily.
Sew the handle on.
But sew yours on the other way. My husband says the balloon will launch farther if the handle is sewn on going "up and down" rather than "side to side." But I gave up on picking at the string on this terri cloth!
Run the tubing through and tie it in a triple knot at the ends.
My boys can make the balloons go about 50 feet, and my husband can make them go over our house.