Planet Bike has a QR band , and a size adjustment, so If you Buy One of those lights with the right mount,
the light quickly dis mounts from the band, then the band mount comes off the Bars. takes a moment longer..

This Year they have a 2 watt LED, I have a 1 w it's reasonably bright, there is a 1/2w version too,
it offers a very long run time per battery/battery charge.