Here's a link for the Thermal R&D three inch exhaust MMRUSA. You should be able to get a custom three inch DP from any decent muffler shop. I know you wanted a prefab DP, but thats the best I can do. You might try Lovefab.com and see if they will make one for you, but you would have to contact them since there isn't really anything on their site for that. They do have some badass turbo manifolds though!!!