I bought a 36 in clamp from box store like these,
https://www.lowes.com/pd/IRWIN-QUICK...Clamp/50137694
They should have a hole at the top end. I had one older one and had to drill a hole, very easy. I Threaded bungee cord (removed the hooks), through the hole, tied a knot and added a small clamp to the other end. Very cheap and works great.