I have a 2015 U.S. Fiat 500 Abarth. I replaced the exhaust with a high flow cat and a 2.5" diameter exhaust system, expecting it to not be too loud. However, I was astounded at how loud it was, considering the stock exhaust doesn't have any kind of muffler or resonator.
Where I live in the U.S. the cops don't mind loud exhausts, but my Fiat was unreasonable and since I like to speed a little bit, I thought I had better tone things down before I got arrested.
The simple answer was to buy a 14" straight through resonator and weld it into the exhaust pipe more or less below the driver seat. The reduction in noise was impressive and now I have a pleasant exhaust note not too far from what the stock car was like with it's restrictive cat and small diameter exhaust tubing. The fix was cheap, easy, and resulted in just the kind of noise reduction I wanted.
Why not measure your mid-pipe diameter and buy an appropriate straight-through resonator and either weld it in yourself or take it to a muffler shop and have some else do it?