Have you looked at Ferme de St Marthe and their 21 chilis?
https://www.fermedesaintemarthe.com/search.aspx?q=Piment
If they don’t do it for you then rather than looking for a seed supplier that has the same sort of range that is regularly found in the UK, search for specific things.
Like kalettes…
(We’ve just eaten the last of ours tonight…3 plants have kept us going since December!)
I’ve ended up buying from Bulgaria and Holland…