I have the Smart Cords with the mute button which have four wires, but it only needs the two center wires for power. I forget which wire is which; I just used a multimeter on the cigarette lighter cord to see how that's rigged up - I believe the contact on the bottom is for power and the ones on the side are for ground.
...But I only had to do that this one time that I got a new vehicle and was too impatient to wait for a proper kit so I built a cord myself. From looking at the ebay page it looks like the cord you have already has color coded wires built into it, so unless they screwed it up when making it, you should just be able to hook the red wire up to the power and the black wire up to a good ground somewhere and it'll work.
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