I haven't seen any made out of the mid pipes. I did however buy a set of "slip ones" that slip onto the header pipe where the mid pipe does. They are about 7.5 inches long and look like an auto exhaust tip with a baffle and race resonator welded inside. The welds are not very clean but they tuck so far up under the bike that you can not see them. They are very loud and have cool growl. They sound like a race car. After paying for them, I am sure they can be made at home for less than $100 bucks and better, if you are a good welder. I know I am going to get a lot of haters for admitting that I bought these but I like them for now.
2009 ZX-14
Semper Fidelis
Kill 'em all, let God sort 'em out.
Violence Solves Everything.