I have checked the AD&D books Netheril: Empire of Magic and Lost Empires of Faerun, and the 3E book Grand History of the Realms.
Are there any official maps of the Seventon Alliance and the locations of the seven towns?
Role-playing Games Stack Exchange is a question and answer site for gamemasters and players of tabletop, paper-and-pencil role-playing games. It only takes a minute to sign up.Sign up to join this community
The location of the towns in the Seventon Alliance can actually be seen in the two poster maps ("Netheril at its Height: The Golden Age" and "Netheril at the Fall: 3520 NY") that come with the Netheril: Empire of Magic boxed set. They are to the north and east of what later turns into the Anauroch Desert on the eastern shore of the narrow sea.