If you cannot find white gull recipe on sale anywhere (Herbalist White Orchard, Gremlist the druid on Skellige etc) then it may well be that you.
Keira Metz – You will find the North from Midcopse considering the same name known as (M4). Oh yeah and someone pointed out a vendor later in the game sells White Gull so if you missed it in White Orchard you can get it then. Check Keira (if she's still available), Tomira in White Orchard, the halfing alchemist who has his own hut west of.
Manuscript page: White Gull is an alchemy formula in The Witcher 3: Wild Hunt that is needed to craft White Gull. Toussaint – There is an alchemist in Beauclair. Velen – Halfling Alchemist in the hut west of Oxtenfurt.