i bought me a leather flip-cover i found on etsy.com
I’m very happy with it.
https://www.etsy.com/de/listing/745687273/fairphone3-hulle-flip-cover?ga_order=most_relevant&ga_search_type=all&ga_view_type=gallery&ga_search_query=Fairphone+3&ref=sr_gallery-1-2&organic_search_click=1&bes=1&col=1