I finished the Dark Brotherhood, so the guy who sold me invisibility potions is dead. Is there any place where I can get them? I heard the new people on the Brotherhood Sanctuary also have them, but I am not sure.
You can make them pretty easily, I know wormwood leaves has invisibility as its first or second effect. Also, try the main ingredient, the gilded carafe, all things alchemical, or one of those other potion selling people who I'm too lazy to think of. Also, 100% chameleon>invisibility and its pretty easy to get.