Forsaken Cave, in the sanctum of the White Phial during the quest 'The White Phial'. It is displayed prominently in the room along with a number of various alchemical reagents and an alchemy lab.
The quest item for the quest 'The White Phial'. Given to Nurelion at the completion of the quest. It is later repaired in the quest 'Repairing the Phial', but it is the empty version of the Phial that is received at the completion of the quest.
Both the empty phial and the replica can be displayed.
You need to have the empty phial in your inventory for the replica recipe to be unlocked.