Here are the known forts where you will find some shadowbanish wine.

Fort Aurus — A small fort northeast of Bravil, across the Niben Bay.

Fort Carmala — A small fort between Chorrol and Skingrad.

Fort Dirich — A small fort between Skingrad and Chorrol.

Fort Grief — A medium fort northeast of Bravil. It's the only fort where the wine
container will be on the outside of the fort instead of inside.

Fort Irony — A small fort southeast of Bravil.

Fort Magia — A medium fort east of the Imperial City.

Fort Scinia — A medium fort east of Cheydinhal.

Fort Vlastarus — A small fort east of Skingrad.

Additionally, if you have the DLCs you can find some shadowbanish wine at these places.

Frostcrag Spire — A tower east of Bruma. In the vault in a wine rack.

Battlehorn Castle — A large castle west of Chorrol. In the wine cellar.