The wiring is in the 2004 as noted above. I would expect if the cable had been included with your truck when new, you would have already found it. Most new brake controllers can be ordered with the appropriate connector for your vehicle. I would recommend this, not the universal type where you have to figure out the wiring, and the connectors. I've tried 3 or 4 different brand name controllers, and I would highly recommend the Tekonsha Prodigy. It's the only one that is noticably different, and better.

Forgot to mention, you need to verify your hitch/trailer wiring is the 7 pin type. A 4 pin doesn't include brakes. See this link for the wiring diagram.
http://www.marksrv.com/wiring.htm
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Listen to what this guy has said! I strongly recommend what he is telling you.

If you search around Ebay for the Prodigy, you can get a good deal on it. I picked mine up for 90 shipped! It is by far the best one on the market for the money!