I know the Specialized Flux mounts so the light hangs below the handlebars:
https://www.specialized.com/ca/en/fl...=220690-132989

Busch & Müller Eyc. It's so tiny, you can barely see it. You need a dynamo to power it. That will seem expensive, but it pays off in the long run, since you don't need batteries, and it's durable.

I know that Knogs newest line has a pretty prime under handlebar mount https://www.knog.com.au/media/crysta...ts-banner2.jpg