There are 3 silencers on an S2, I take it you are referring to the first silencer splitting down the middle? If so this was a cat on some cars, looking like this:
You could go for a generic pattern cat but whilst this would not matter on an S2 I tend to find that they make a modern car fail badly at emissions after a year of use, and that is before you get to them being more restrictive than a stock item (this occurred to me on a few cars now. I understand that this issue is far worse with modern DPFs but we shall leave this discussion for another time
.If it is the cat that has gone on your car I would be tempted to either go to ProMax for a replacement Cat Bypass section, or go along to an exhaust builder who will fit either a normal silencer or a straight bit of pipe should you desire. A number of racers do the latter here.