Oh my, so much discussion over Bart's and EMG's..... I honestly don't care what the builder was thinking about the tone, or what builder it is as long as I like the tone of the pickup. That being said, I love almost every Bart I've played on or heard and the DC series of EMG is tonally pleasing to my ears, while I HATE the HZ's. I'm very interested in the Extended Bass series, but have yet to play a bass with them.
BUT, if you wouldn't mind stepping away from those manufacturers, I'd like to suggest some other companies. Take a look at Lindy Fralins. The stock pickups are really nice; I have yet to hear a custom wound pair. Lindy will wind pickups to suit you and your personal tone, so if you talk to someone in the shop I'm sure they'll be happy to help you get it wound so that you like it.
http://www.fralinpickups.com/
Carey Nordstrand has quite a wide variety of pickups, and is a reknowned builder himself! He's quite the nice person, but I haven't played any of his basses or pickups personally. I have read countless reviews of both his basses and his pickups and I haven't seen anything negative. A good friend of mine swears by Carey's MM style pickups (I believe the specific model was the MM 4.2?). He even sold the legendary Lane Poors out of his Modulus Flea in favor of them. Every sound clip I've heard has had amazing tone. I'd also suggest calling him if you're interested.
http://www.nordstrandguitars.com/
Aero pickups are also an alternative. I personally didn't like their tone too much, but many others do. I don't know much about the company myself, so I'm not going to say I do.
http://www.aeroinstrument.com/
Fralin and Nordstrand pickups are both available from contacting them through their sites (I think?), or from http://www.bestbassgear.com/ .
I don't know where to get Aero's from, probably their site as well, but I'm not sure because I personally haven't looked around.