Most of us who cycle a lot or use the bike to commute have got removable bicycle light that run on batteries. They’re great: Small, mostly waterproof, available across a wide price spectrum, mostly bright, and most importantly, they’re removable. taking the lights off the bike when parked up somewhere is simplest means of not having them stolen.
But with this solution arrives a big problem: each manufacturer uses a proprietary fitting system, that is often not even compatible between different models of the same manufacturer. So if you ever want to take the light onto your second/friends/new bike you’ve got a problem. You’ve got the lights but no way of fixing them. Plus, most fittings are constructed so poorly that they will rattle loose which leaves the bikes either brightening up the night sky, or the floor beneath the handlebar – both options are neither safe, nor an excuse that’ll get you out of a fine if the old Bill stops you.
So I came up with a very effective solution: A small piece of 5mm bungy rope, tied into a loop. Stick the end of the light through the loop, feed the doubled-up strands underneath the handlebar, and slip it over the front of the light.
To secure it all, feed the end of the loop with the knot underneath the opposite loop, and your light fixed rattle proof, removable and reliably to you bike. I’ve been riding like this for over two years (nearly daily) without a hitch.
I’ve even mounted my Exposure Flash to my helmet this way, avoiding the pricey helmet mount. This should work with pretty much any front or back light that is more or less cylindrical in shape.