There are plenty of great options available. Bartolini, Fender, EMG, Seymour Duncan, Lindy Fralin to name a few. I recently swapped my Jazz Bass pickups for a set of Lindy Fralin and love the way my bass sounds.
If you want to add a J pick up you will need a router to cut a hole for it. If this is something that you are not familiar with, I would recommend bringing the bass to someone who has experience making this kind of modification.
"If you don't want the truth don't ask. Make up your own like everyone else does". (Michael Pare as Eddie Wilson/Joe West in Eddie and The Cruisers II).