Try this: enter search term "Nikon F" + body into the category "Cameras and Photo". Go to advanced search and enter this string in the "Exclude words from your search" field:
F2 F2AS F3 F4 F5 F6 F100 F90X F50 F65 FinePix F80 F801 F70 F401 F301 F75 F801 F601
This resulted in 114 "hits" for me just now. Most everything is either a Nikon F camera body, or lens caps. There are a few additional camera types that still show up, if you wish add them to the field to exclude from your search.