OK so i did some online research and it seems that both bars- upper and lower can be bought online.
the rear upper bar >>
http://www.ebay.com/itm/Aluminum-Strut- ... 6a&vxp=mtrthe rear lower bar was bit more tricky in the sense that it had 3 brands addco, whiteline and progress.
stillen would have been awesome but they dont make the bar anymore..
the progress is the best choice- from the research done - its from the 95-99 maxima a heavier car than the P11 and it works - bolt for bolt- its THICKER as its ment for the maxima( heavier car) but not as heavy as the u14/P11 - therefore the torsion force will be greater meaning less body roll which in turn means HARDER cornering...
the rear lower sway bar >>>
http://www.cattman.com/ the kit # CRSB-G4/5
called TSC and he indicated that he had the megan racing bars... thicker and more solid than the generic so i'll be heading down there to take a look.