On my Yamaha BB1025X, the bridge J pup is louder than the P, and combined together they sound glorious and full!
Perhaps an Entwhistle neo pickup.. only £10 and from what I've heard, just about the loudest you can get?
[url="http://www.entwistlepickups.com/pickup.php?puid=JBX"]http://www.entwistle...up.php?puid=JBX[/url]
(EDIT: It appears the JBXN is the neo one and seems to no longer be made, not sure how the JBX compares)
If not that, then the Seymour Duncan quarter pounder.