I got Thundercat 4-2-1 front pipes on mine (stainless aftermarket, make unknown) and they fit straight on the FZR, barring some minor bracket wizardry at the rear support/mount under the engine, just forward of the swingarm pivot. R6 front pipes can be modified to fit and are becoming popular.
Once the fronts are sorted, be they FZR, FZR-R, Thundercat or modded R6, then you've a huge choice of end cans - so long as the diameter of the clamp end is the same, and you can fit or make a bracket to support it, virtually anything'll go. I have a Carbon Can Co stainless oval originally intended for an early R6.
Not the best pic, but it shows what is easily achieved...
