Lezyne has adapters for their lights, there's a list of compatible ones: https://ride.lezyne.com/products/1-led-gpad-v104

I don't know about availability in the EU, but I like this one:

https://www.amazon.com/gp/product/B0BFKH2J63

This brand could also be an option:

https://magicshine.com/

I have an older exposure trace. Really nice light for all year round, good day flash that lasts a good while, and in a pinch can be used to illuminate the road(would suggest something brighter for longer rides though).

Only downside is the charger is usb micro on mine, but it has been updated to USB C now.

https://www.exposurelights.com/products/boost-daybright-mk2-gun-metal-black

Would something like this work (just strap it to your handlebars/stem)

Otherwise, i imagine most major manufacturers will have go pro adapters (or third party ones) to adapt.

I used a 3d printed adapter for a cat eye light for a while

NiteRider has a K-Edge adapter for their Lumina lights:
https://www.niterider.com/products/gopro-adapter-by-k-edge

They're a US company but have distributors in Europe.

The Luminas are a more serious headlight than you are looking for. They're great, though. Mine lights up the road on the darkest nights.

A provis/reflective jacket and any low, wide beam light aimed at your chest. (I actually have no idea, but the above is an idea I've thought about before. Downside is a light kinda shining in ur eyes...)