None of these work? The have 3', 6' and 10' cables for USB to 30-pin dock connector.
»www.monoprice.com/produc ··· =1083101
If not, what exactly are you looking for? What ends, color, and length?
If you're looking for 30-pin female to 30-pin male, I've never seen or heard of one and would wonder about it's use...
 Nevermind they're called "dock extension cables":
»www.amazon.com/30-pin-Ma ··· 04BAC2B0
»encrypted.google.com/sea ··· %20cable