Search each in the database for exact drop locations (most are world drops after level 40).
Before we dive into specific websites and legendary items, let's address the elephant in the room: Torchlight 2 uses a "smart loot" system, but it is still brutally random. You might play for 200 hours and never see a Winter’s Tendril or a Skull of Limoany . torchlight 2 item database best