Gastank auffüllen

Kosan Gas might be an option – they have retailers and gas replacement centers all over Denmark. Link: https://www.kosangas.dk/privat/koeb-og-ombytning/find-forhandler/find-din-naermeste-forhandler-eller-gasautomat/ (in Danish – you might want to google translate the page).

Not sure they refill or exchange tanks that aren’t their own, but you should at least be able to buy a new one even if the old one can’t be refilled.