https://www.cargraphic.de/en/?C=EUR
Or you can try these guys, I have their complete system including excellent cats, their active switching system, GT3 style muffler all custom made to my car for not a horrendous sum of money considering.
Call Thomas Schnaar.....he knows his stuff and in particular, he has an earlier 911 and a wife who hates droning sounds, so he worked during the development phase to ensure that there was no spouse related objections to driving around.
I love mine - on an ITB/Motec 3.4
D.