I have an iPod that uses a 30-pin dock connector. I have a vehicle that has a 30-pin cable built-in to connect the iPod to the vehicle's stereo. But the stereo does not provide power to the iPod. Is there an adapter so that I can plug the vehicle cable into adapter (for data) and a USB cable into the adapter (for power)? I intend to get power from the vehicles DC outlet and an adapter to convert to USB.
I think you have the wrong idea here.
The 30-pin connector for an iPhone has power and data ports. Your car clearly is not serving power to the power port of your iPhone connector. To do this manually, I'd recommend taking a look at the link below. It is based on giving power to a VGA accessory in order to power up the iPhone with this same plug. You are basically trying to do the same thing with a music adapter for your car.
Hope this helps! (If it does, mark it as the answer. Thx.)
Ah, found what I'm looking for. I originally searched for "40 pin power injector" and didn't get any obvious good hits on Google. But it turns out I should have searched for "30 pin power injector".
CableJive dockStubz+ seems to be the product I was looking for.