The following link is to Parts-People which stocks genuine Dell parts. They seem to be out of stock now but possibly you can contact them for inventory updates. Also I believe they ship worldwide.
https://www.parts-people.com/index.php?action=item&id=24233
Also, and they have warehouses in Europe.
https://www.canada-laptop-battery.com/canada-battery-dell-6097.html#
Thank you for the answer.
https://www.parts-people.com/index.php?action=item&id=24233
It says that this battery was used in the item description. I therefore assume that this is not a new battery.
This one seems to be new https://www.canada-laptop-battery.com/canada-battery-dell-6097.html# . Does anyone know its manufacturer?
It seems that I have also found the original version https://www.amazon.de/gp/offer-listing/B07PJ3C6MX/ref=dp_olp_new?ie=UTF8&condition=new from Dell. Its a little more expensive.
I also recommend that you undervolt your CPU. Search how to do it with ThrottleStop, and then search undervolting for XPS 13