Correction Brummkreisel (sorry, don't be mad about it):
Yesterday, I called the Company Fox. They told me, they'd offer an endmuffler for 350€. That's what the women on the phone told me (strangely, the endmuffler doesn't appear in the online shop; there are only endpipes for Materia offered). Unfortunately, I dind't ask for the end pipes. They don't offer the rest of the exhaus system (from catalyser to endmuffler), but they could build it for 250€, but you'd have to bring your car to them, cause it's handmade.
Just contact them:
Info@fox-sportauspuff.de