I bought the bolts from a local motor factors, but they only had the black ones. You might find the stainless ones by looking in your trusty Yellow Pages under Fixings & Fastenings or Bolt & Nut Stockists. Incidentally, the Nissan engineers probably went with screws rather than a bolt to keep someone from stripping the threads or warping the cover by tightening down on them too much. Haynes says 2 lbf ft of torque for the cam cover screws which really isn't that much. You don't need a half inch drive ratchet or a torque wrench. Follow the sequence for loosening/tightening the screws as in the Haynes manual also.
The paint isn't wrinkled but the cover was slightly pitted, as most of them are, so the finish isn't that slick. Better than before, however.
S