Scion iPod cables
There are three cables required for the stock setup.
One connects to the rear of the head unit and mates with another cable under the console that ihas the console connector on the other end. Then there is another connector that plugs into the console connector and connects to the iPod.
In a 2007 Scion the cables should be there,
The head unit cable is part of the main harness.
I believe that it is only the 2005's that do not have this harness.
There is a person that sells Scion iPod cables on ebay usually.
They are under SC12234 and SC12235.
If I can help you more contact me