An extremely low drop from Uldaman dungeon creatures. May still be in the game, but I really doubt it still drops. Even if you exclude WoWDB (which is silly, but whatever) due to its young age as a database, Wowhead does not list any source for the item - even though it used to have such a list prior to Cataclysm. The single Wowhead comment claiming that he/she looted it post-Shattering is dubious when considering the claim dates it to Patch 5.1 when the comment was posted two entire patches later (in Patch 5.3.0).
This item is/was the only fez in the game with a solid red color. If you do happen to spot it in the Auction House, expect to pay a really really pretty gold coin for it if the seller knows its true value.