Bartholomew Watkins seems to be an underhanded fella. He can be found hiding in the alley next to Truehound's Tailor Shop on Port Royal. Not much is known about this shady character, except that he obviously fears being discovered or being seen in the company of known pirates.
These goods are obtained by attacking various ships. Bart's quests reset after being completed, so the pirate can do them over and over again.