You could put in a Mufflex kit, which is a bolt in muffler swap. Cherry bomb makes one too, just a different sound. You could also have an exhaust shop cut and weld in any muffler you want. I had a shop "build" me a catback for around 250 bucks, new muffler, better Y-pipe and retained stock exhaust tips and resonators through the bumper. Flows great, sounds great.
My custom job, mine used a 18" magnaflow muffler, just like the DOD18M mufflex
Mufflex bolt in mufflers, 3 sound choices