I'm looking for a car holder with USB pass-through ...
The only one I found so far is the one by ProClip.
(TomTom carkit doesn't qualify because the USB only transfers power, not data => no pass-through)
That's not right. The TomTom car kit transfers everything except the audio for voice calls. And that's because Apple doesn't allow voice audio over the bottom port connection. You won't be able to get voice call audio passed through that connection no matter what you use.
I use this and love it:
http://www.tigerdirect.com/applicat...CODE=GOOGLEBASE&cm_mmc_o=VRqCjC7BBTkwCjCECjCE
Fits everything including if your using a case.