To be honest I think keeping an eye on uk/german ebay for a GSR kit might be your best bet, I think the one on the forum would use mainly the original pipes with the cone in place of the original air filter housing. Are you getting rubbing over speed bumps? I'm 99% certain its not your exhaust, but your engine undertray. Mine had a couple of clips missing so it used to scrape a lot, but even now with it properly secured going over some speed bumps very slowly it still scrapes! Just take a look under the engine where the plastic shield drops low a one point, and you will most likely see that its scraped.
The undertray on my bravo hits everything and I'm in a dynamic model. Which is higher than a sport I believe. It doesn't really catch the main speed bumps (sleeping policemen) as much. But it catches the speed cushions (smaller ones that don't go right across the road) nearly everyone whether in doing 1MPH or 40. I've resorted to hitting them off centre so my passenger side lifts up and over them. Not so comfortable for my passengers but makes my life better not hearing that god awful row as it scrapes along the hump. (I'd like to point out I don't hit bumps at 40mph I was exaggerating lol)
Whilst I'm in this thread though. If I was to have an aftermarket exhaust fitted could I have it come through the rear bumper like the sport model? At the moment mine is folded behind the rear bumper. But I do love the look of the exhaust on yours.