I'm a Corsa fan, but since they discontinued their black box and red box mufflers you can only get them used. It took me 3 years to find 3 mufflers and I got lucky and met the man who runs their production line. He had them behind his desk new in the boxes.

Other than that is comes down to dimensions and the material you wish to use. There are far more choices if you are willing to use Mild steel.