I don't know if anything is out there that replaces the stock look for exhaust headers. The doubt the demand is there for anyone to manufacture something like that.
To make the car louder you just need to replace the muffler assembly with something louder. As mentioned above Brian at RarlyL8 has four, or more, options for sound level and they will all bolt to your current turbo.
RarlyL8 Muffler systems for Porsche 930