Ti-Force, who are out of business.
Akropovic, which are smaller.
These are both 4 into an "X" pipe into 2 mufflers. They are the only two exhausts that could really be called a 4 into 2 into i back out to 2.
Vance&Hines makes a 4 into 2 with a cross over, "H" pipe. V&H, stock, and any aftermarket gen2 mufflers will bolt to the V&H headers also.
No one else makes a full dual exhaust for the gen2.
You would need to modify/remove catalytic converter on the stock header, or make your own.
There are many dual mufflers avaiable for the stock headers.
Mufflers in general, with the largest pipe diameter will be Ti-Force, HMF, and possibly a few others(everyone makes mufflers).