I started using reusable cable tie wraps when I lost the Lezyne rubber piece. The link if or 12 inch but you can buy whatever size you want.
https://www.amazon.com/HOTUN-Reusabl...s%2C191&sr=1-3
I can pull it snug around the light and seat post such that the light stays in place. I may work with the aero integrated post.