I wanted to build my own simple exhaust rom the cat back, so I bought a cheapo muffler and some straight and pre bent exhaust tubing.
The muffler was really cheap, like $35 bucks. I think it was called a magnaflow. It is a small single chamber muffler. Dimensions are about 10"x12"x4", with a 2.5" inlet/outlet. It tucked up and hanged nicely, got it spitting out the side in front of the rear tire, nascar style.
Also I ordered a "Gianelli" cheapo full exhaust for my Yamaha R1 many years ago and also have been very happy with that.
I'd wish you luck, but you probably won't need it, should be fine. Post back results, cheers.