I've got this resistance tubing with hand paddles. They have a wrist strap and a single finger strap that your middle finger slides into and the middle finger strap works really well. It keeps the paddle tight to your hand which you need when your palms are all sweaty. Just an idea. Ankle strap from an old leash for a wrist strap?

http://www.kiefer.com/kiefer-dryland...hp?page_id=237