8Th Gen Corolla Exhaust

Should be able to find a number of places that would sell those exhaust. They might not have the whole assembly, but definitely have the components to make it up (ie, resonator, tubing, muffler, tailpipe).

Could get a muffler shop to build one up for you, at a considerable cost savings. Just pick up a muffler you like, have them make up the rest of the exhaust with mandrel bends in tubing of your choice.

For a sound point of view - muffler will have the greatest influence in sound color (bright and tinning, flat and blatty, etc), the resonator (between cat and muffler) will help shift the frequency pitch and overall loudness of the exhaust. Generally, need to do some experimenting with the exhaust components and tubing length to get just the right amount of sound / type of sound you want. Just keep in mind that there is a limit to what sounds you can get - no exhaust will make a Corolla have the sound of the bright timbre of a Ferrari or the low rumble of a V8.

For a performance gain - spend your money elsewhere. Unless there are extensive mods to the engine, many catbacks will likely LOSE power, than gain it. The current exhaust system is actually pretty efficient, you already have a tubular exhaust manifold vs the conventional log type cast manifolds. Exhaust scavenging is much more critical aspect to performance and generally has to be engineered to. Can't just throw on a bigger diameter exhaust piping, mandrel bends, and cannon exhaust of a typical catback setup and expect the scavenging to be optimal.