Just a few words of caution:

I took a look on the web for various Canoe Leashes and found they used Velcro or Velcro style wraps, either around the wrist, ankle or waist. If you decide to use one, take great care in their use around any moving water, including strong currents and tides. A 71-year-old man or any individual with limited strength may not have the ability to fight or counter act the force applied to a large surface area such as boat and find themselves being dragged with the current/tide. The use of a weak link in the system would be advisable, even with a Velcro attachment point.

Never, never, never hard tie any item to your person or PFD in moving (swift) water, always have a weak link built into the leash/lanyard.

Pete