They're not boat rigging specific, but I've had really good luck with these guys. Active Electronics.
http://www.active123.com/
They're in the northeast off 32nd Ave. Chances are very good they'll have what you're looking for, and if not, they can get it real quick. The other bonus is the staff is very experienced, and they've been great with answering all my questions and making sure I had what I needed to do the job properly.