I took the alternator apart to get the regulator out of it. I know it was there. I suggest you check your sources on that one. Believe me, there is precious little I will ever forget about that piece of crap automobile.
The parts store. It was probably under warranty, but I'd been fscked by the car dealer several times before this as regards the warranty, and I couldn't afford to let them keep it for a week or two while they diagnosed the problem and another week or two while they waited for parts (if indeed they found the problem instead of returning it to me broken, "no problem found").