Paul made this bar clamp from a modified bungie clip found at Harbor Freight. Just pull the red ball over the bar and lock into the clip below. Hanging off of it you can also see his stylus that he uses for his tablet computer (so the bungie cord provide dual functions).
The bar clamp isn't super strong, but it's very quick- giving you some time / help to get more clamps / ties on the trike, or just an extra hand while you're in the cockpit doing things on the ground