You can probably get them at just about any muffler shop or from a performce shop such as Jegs, Summit Racing, or even JCWhitney. Or you may be better of just getting one of the many Cat-backs they have out for our cars right now. It may also be helpful for you to check (post) with the people in the specific Michigan forums. Not sure where Dearborn is, but I know some of them could probably help you out with a good muffler shop in your area.
p.s.- Or you can find someone selling an SVT exhaust. Cheap and worthwhile upgrade. Check the classifieds for that.