After looking in several stores for a ready-made cable and only finding one for $50, I decided to make my own. I found an iPod connector easy enough (about $14), but the small, flexible 5-conductor shielded cable surprisingly proved much more difficult.
I then came across LightInTheBox.com - and there was a ready made cable for less than half the cost of the connector alone - I purchased three. One I used as is for the stereo. The 2nd I am using for the transmitter project. The 3rd I am keeping for some future use or as a gift.