I was going to suggest Planet Bike, they have several versions of the Superflash that use two AAA batteries, but sounds like that is not an option. But if you wanted to contact them and ask if there is a retailer in Europe, they are at:
https://www.planetbike.com/support/#contact-us-page
The Busch & Muller lights that I have used are all dyno powered, but they might make some battery ones. It however is possible that none of theirs flash since they are made for the German market.
https://www.bumm.de/en/