Right now there are no bolt on exhaust catbacks for Bonneville'*. You have two options, if you want to do it immediately, you can go get a custom job done at an exhaust shop which will run you about $300 dollars depending on the shop and the muffler you choose. I own Angry Duck Tofu Racing and later we will be developing a catback for the Bonneville'* and Grand Prix'* that dont cost over $500, it will be more like $300 w/ stainless steel tips. So you can either be patient or do a custom job. Hope that helps.
ADTR 1999 Black Bonneville SE
2003.5 Yellow Mazdaspeed Protege
2003 Azure Blue Mach 1 Mustang