Dealers only - If you're talking about the cable that connects up to the back of the MID to enable AUX. You can make your own if you're electrically inclined...Google for the instructions. You'll just need couple of capacitors, resistor, wires and the 3.5mm input jack. This site should have the AUX installation instruction to give you information on the pinout.

Any electronic stores - If you're talking about the 3.5mm/3.5mm stereo cable that connects to the AUX input jack.