Ah...not my area at all. I've only been to Port Jeff once. Never to Port Jeff Station. I fish in Riverhead regularly, but that's quite a bit south.
And I've never gone that far east on bike.

In any case, good luck with the dog. I'd get some mace if you run into him again. Sports Authority or Dick's will carry it at the gun section. If you go to a real gun shop, they might have more variety, maybe something designed for dogs. I don't know about repellents, though.