OP - you've perhaps unknowingly stumbled upon a religious topic here. People on this board are so obsessive about purity in P-bass tone that they'll argue that a PJ bass with the P pickup soloed won't sound correct because the J pickup is there and is magnetically affecting the vibration of the string in a way that would not be happening were it absent. It's something to observe. As a practical matter, soloing the bridge pickup on a jazz bass and perhaps adding some midrange in the EQ will get you close. Might want to focus on a vintage-designed set of J pickups, as those might be less scooped than something with a modern approach. Like Fender vintage 60s pickups versus Sadowsky humcancelling pickups. You won't fool anyone in a recording studio that way, but if you're playing a cover tune at a show (for instance) where the original used a P-bass and you want that chunky sound out of your J, you can get by.