I recently tried a new prodcut called APALS; All Purpose Adhesive Light Strips-AIR on the back of my PFD and the bow and sides of my Kayak. These are waterproof thin LED lights with intergrated battery that are encased in a waterproof sleeve and have a peel off adhesive that sticks to anything.
They com ein colors so I use white for the top bow and red for port side and green for starboard side. I used amber for the back of my PDF. These can be set to fast strobe, slow strobe, steady on or off and run for around 70 hours. The are super thing and weigh less than half an ounce. These are made for the military but work great for night time safety for kayakers.