Cohai: Thank you for all your help.
Unlike my last try at the game, 2 years or so ago, the alchemy bug has been fixed and travelling much further afield has found other formulae. Still to find essence of grace, but will keep travelling
You'll never buy essog.
your "4 formulas" problem is actually a 22 formulas problem, where the sources are selling only the first 22 indexed formulas of the total 66 formulas in the game. This was an error made by the designers- they thought oh there's 22 different kinds of potions, and they sort of forgot that there were 3 entries (25, 35, 45q) associated with each.
The remaining 44 recipes you can never buy start at #23 (35q thunderbolt) and end with #66 (45q firewall). Here is the list of potions in their INDEX order. You will only buy Nox through 25q Thunder, 22 recipes.
Noxious Aroma
Eyeburn
Black Cloud
Fleadust
Eater Water
Breath of Death
Sunburst
Thunderbolt
Arabian Fire
Stone-tar
Deadly Blade
Strongedge
Greatpower
Trueflight
Hardarmor
Transformation
Truesight
New-wind
Ironarm
Quickmove
Essence o'Grace
Firewall
Where to get the other 44 formulas? Only by the option "trading alchemical knowledge and formulas," which can produce a random one.
This is not the sort of bug GOG has any responsibility for and could only be fixed by reverse-engineering the game.