Carsten,
You wouldn't find an original exhaust anywhere. Possibly a half decent 2nd hand one, but it would cost you a fortune.
You'd be best thinking of a new exaust as being the final finishing touch to your project. Along with new rear shockies it will be a big investment so you'll want to know that everything else it tip top before you spend 700 on an exhaust and 3-500 on shockies.