USB power in your car.

 I am guessing that one need not have a 2010 Prius lying around for parts.

Once again my 24v vehicle needs more stuff to make all the other stuff run.

 I think you should do it Ben.  I recently rented a car while traveling and it had, not only a USB port in it but also a 110 style receptacle.  Kind of cool.  It was some kind of Ford.  Plus in your iPod and the stereo (Microsoft's Sync platform) and it recognized everything right away.  Very cool.