I really liked my Lezyne megadrive. Great design, very bright at 1200 lumen, but it would just not fit in my cockpit with hydraulic brake cables etc. And their newer designs do not have the dame features (field replaceable lithium batteries and clever mechanism of waterproofing of the battery. They are still good I am sure,.

No I use a garmin varia Ut800. At 800 lumen it is not as bright as the Lezyne. Also the battery has a limited duration and is not field replaceable - but good enough for my 30 mi RT commute ( a good part on unlit paths and through woods in Chicagoland). Most important, It has a go pro mount and mounts under my garmin 520 mount. An added feature is it can be controlled by the 520 and has a number of different modes (including based on speed) and it has a good flashing mode for visibility that lasts a long time. The light can be taken off or attached easily with just a twist of the mounting ring (which you can see in the attached photo - the knurled ring above the light).. I can also mount it in my k-edge garmin mount on my road bike. You can mount it on any bar accessory that has the correct orientation go pro undermount.

Not sure if you are looking for anything like this, but thought I'd trow it in.