I made a mount from a 1x2 piece of wood scrap (actually more like 0.75" x 1.5").
I cut it in half lengthwise to get two pieces 0.75" x 0.75" x 5" long, then cut a notch on each piece to go around the handlebar and clamp onto it with force provided by velcro and/or elastic strips.
I cut notches around the wood bars for those strips of velcro on the front and the rear side. I painted the wood black. Then I wrapped a strip of old innertube around the handlebar to give some friction. The flashlights get held on to the wood bars with more velcro strips.
I can use 1 to 4 flashlights (I have 2 Fenix L2D's usually), and I can move the wood bars up or down to aim the light as needed. It's a kluge, but works fine and the lights come on or off fast.