I have a UK SL4 light I take with me on all dives (daytime or backup night light), but it's too big to fit through a bicycle inner tube. I use surgical tubing tied into a loop that goes through my right shoulder D-ring so the light doesn't dangle when not in use. There's a lanyard that came with the light that I clip through a stainless carabiner that also goes on the D-ring, so if I let go of the light it just dangles. It's simple enough my wife uses the same setup.