Mini USB / HTC extension cable

[jonnythan]

So I need the wizards here to help me out.

I need a mini-USB or HTC extension cable that will support audio and power.

The intent is to have a car installation that only has one cable going from inside the dash to the phone. Right now, I have a mini USB power cable and audio cable both going to the adapter box for the phone, which is a huge mess. I want to hide the adapter box in the dash and just have one cable going to the phone itself.

I'm trying to make my own, but the wires in the included breakout box are painfully short, and the phone is making it difficult to determine which wire is what.

All I need is power, audio left, and audio right to work.

Any tips?