Question about a outfit.

It may be in the pirate emporium. Im not totally sure if it is since i never took a deep look at the pirates life stuff on there. If it isnt in there, then there are only 3 other hooded outfits in the game at the time that i know of. The first being the reaper costume, and the other 2 being the lvl 100 gold hoarder and order of souls costumes, which may not be quite the style you are going for, but are probably the closest alternatives.

The Castaway costume is regrettably not one that is currently available for purchase or unlocking anywhere in-game.

It is indeed! It's a shame too, since basically every other PotC character in the game has had their constume released for purchase in the Emporium.