In the Nikon macro/micro equipment section of this web site some microscopes are mentioned. Since this site is dedicated to photography information on microscopes is very limited. Your camera dealer will not be able to inform you, too, as Nikon microscopes are produced, distributed and sold via a separate company: Nikon Instruments Inc. If you are interested see for more info on this site
Above site will inform you on special microscope cameras, too.
However, there is one Nikon microscope, which unfortunately is only for sale in Japan (despite an english text on its box), is the Nikon Fabre microscoop with the possibility to attach a Nikon Coolpix and/or Nikon digital reflex camera (via adapters). Standard magnification is 20 x, but used on a DX-SLR a magnification of 66 x is possible.