A few years ago another BF member, Timothy H, posted photos of his Light & Motion headlight (one of the Urban series, I think) mounted upside down and under his bike computer. Search his name and the topic and you'll probably find the photo.

Technically Light and Motion recommend against mounting their lights upside down, but I suspect this is over concern that the user might forget to replace the soft plastic/hard rubber cap over the USB charging port. I've mounted my L&M Urban 500 and Rando 500 upside down and sideways, ridden in rain, no problem -- the USB cap seals out rain.

There are also generic velcro strap mounts with rubber blocks in various configurations that enable versatile mounting. They aren't pretty or slim but functional and inexpensive. I've had one for years and it's really handy for improvised mounting, such as when I needed to get around or over a handlebar bag that blocked the supplied rubber band type mounts.

If I ever get a 3D printer, first thing I'll do is make my own mounts for lights and cameras. Mounts are often the weak point even in the better bike headlights and action/traffic documentary cameras. Taillight mounts are usually okay.