Hey I don't know if OP still wants info on Tarr basses, but there are two that I know of (three if you include the other Halle Tarr mentioned in Ken's page).
Ken Smith currently has a Halle Tarr in his shop, full details here:
Tarr Bass
As well, there was another Tarr that I got to personally try out back in 2012, at David Gage's shop. I can't find any pictures of it online, but it's a smaller gamba model, which I assume was blonde when it was new but is now a more faded shade of beige. It was once owned by Ed Tait, who has been retired from the Toronto symphony for a number of years. Last I heard it was bought out by either a serious student or a young professional, though I don't remember any names.
I believe the neck of this bass had been moved either up or down to change the string length. I don't know which direction it was, nor do I know if it was eventually moved back. It now has an extension by Mario Lamarre, though, so I doubt anybody will be moving it again anytime soon.
I only played that bass for about 2-3 minutes (I was shopping for a less expensive bass). It was set up with Belcantos, hard to play in the solo register since the action was set a bit high, but in the lower register it basically played itself. It didn't sound like all that much under the ear, but I had a Zoom recorder with me and when I listened back to what I played I was astonished. This thing is a cannon, especially in the lowest notes down to C. And it's easy to get around since it's relatively small. If I had the money, I probably would have gone back and bought it on the spot.