A four string Carl Thompson. The most basic models start at around $4,000. There is also a four year waiting period. Also, Carl no longer takes orders, so the onyl way to get one is to coax the owner into selling it (good luck).
"The first is a 4 string fretted 32" scale piccolo bass made of walnut and mahogany, and fitted with a single EMG-35DC pickup. It has a Kahler tremelo that was later added by Claypool." From the Carl Thompson site.

That's the bass and if you need to know the price you can't afford it. Also like Bumper said they're going to be nearly impossible to come by.
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Those look a lot like the CT basses, a little too much imo.

Like the others have said, it's going to basically impossible to get one since Carl has stopped making them. Plus, the price for one and the waiting period probably adds to sentimental value which means nobody will be selling one anytime soon.

Your best bet is to try out the site that Tallman posted. Those are some classy looking instruments. Even if they are knock-offs.
-Fender Deluxe Active P-bass (60th anniversary)
-Peavey T-40 (1982)
-Hartke HA-3500
-Aguilar GS 2x12
-GK Backline 2x10