I sewed a pocket on to my panier made of mesh. It faces to the rear. I turn on the light and drop it into the pocket.
My problem was different, however. The light didn't mount anywhere and the plastic clip thing on the back of it broke. But it was a bright light that you can see blinking from any direction with a battery that lasts forever so I wanted to salvage it. I could have sewed a clear plastic pocket on, too, but the mesh was easy.