I only ride outside during daylight hours, but I like to use a small front flasher light at all times. My current light is the type that attaches to the handlebar with a rubber strap. I recently added a Garmin GPS computer (Edge 530), and the mount is dual-sided. I would love to get a front light setup that uses the bottom Garmin mount attachment point. I've see adapters for GoPro-style mounts, but the only lights I've seen that would work with this are large, nighttime-type lights, not small ones. Any suggestions?
There are few rechargeable lights with beam shaping and cut-off that may be mounted upside down. Cat-Eye has two in its G-Volt line that come with GoPro adapters. Lezyne also has a light for hanging mount.
GoPro mounts below Garmin (or other head unit) mounts are fairly common.
Below is a picture of a GVolt 70 mounted to a Sigma mount. No adapters or small parts were needed. Both were compatible out of the box. For beam characteristics and review (in German) see Boissier-Mohr's webpage
I’ve built this mount out of some aluminium sheet I had lying around:
It uses the two existing holes in the bottom of the Garmin mount for two small screws. The heads of the screws are inside of the mount (they barely fit in the space below the topside mounting mechanism). The blue stuff is threadlocker.
Sometimes it is impossible to find exactly the combination of features you need in a small part.
Presumably you need a "quarter turn lock" receiver on top to mount with the underside of your garmin mount, and then below that some kind of round "bar" for the light to strap onto ?
But instead of the gopro mount in this picture, you want a round bar?
EDIT: I threw together two options:
In this vertical one I'd suggest you use a ziptie or similar to stop your light dropping off the bottom on a bump.
I had something similar when trying to mount an airzound on drop bars to use from the hoods.
In the end I designed and printed my own mount.