It's not necessary to have a factory plug, so getting one from another vehicle wouldn't be helpful.
There are two common types of brake controllers--an a few now considered uncommon, like the kind that taps into your brake lines. The ones you will see are either time-delay or inertial.
Time delay controllers receive a signal from your brake light switch that you have stepped on the brakes. They then begin to apply current to the trailer brakes, gradually ramping up the current at a set rate. There are two knobs on them--one sets how quickly the current ramps up and the other sets the total power allowed to go to the brakes. These controllers are scary because in a panic stop they just gradually ramp up the current, just like it was a sunny day out. There is a panic bar you could press to get full current, but more than likely you will not have the time, or the extra hand. It's a joke.
The other kind in the inertial. They are 2-3 times the cost--about $100--and they also use the brake light switch to activate them. However, they have an accelerometer in them that senses what the vehicle is doing. If you put on your brakes gently, they give just a little current. If you jam the fukking brakes on with both feet and scream like a woman, they jam the trailer brakes on with both feet and scream like a woman. They have power settings and such to tailor them to your truck/trailer, but the bottom line is that they are use feedback and adjust to what you need while the other electronic-time delay type don't have anything to do with what you are doing.
I have a Prodigy. I'm sure there are competitors out there now, but the best part about the Prodigy when I bought it was that it didn't require leveling. Some of these inertial controllers have a simple pendulum in them. You have to adjust the internal pendulem so it is centered when the controller is at an angle--like mounted under the dash and pointing up slightly so you can see it. The Prodigy doesn't require tinkering with it. The Prodigy has three levels of aggressiveness that you can scroll through. For instance, you might have it on Level 1 while going to pick up a car with an empty trailer. That will keep the trailer tires from skidding everytime you tap the brake pedal. But once you load the trailer you might use the second level for a little more agressive response. It also has a total current adjustment and then there is a manual trigger which I use to pull the trailer straight on a snowy road if the rear of the truck starts to slide--which it occasionally does with a rear locker towing something.
Hooking these up is pretty easy. In a nutshell--you tap into the side of the brakelight switch that isn't always powered; you need a constant heavy 12V source, a heavy ground and a heavy wire that runs back to the trailer connector. By heavy I mean 10 gauge wire. Maybe 12 on a single axle trailer.