I use a searches like this:

nikon f -f6 -f3 -f5 -f100 -f5e -f4 -f2 -ftn -f65 -ft -f60 -f401 -f90 -fe -n4004 -f5 -f70

You can keep adding more "-xxx" to he string as you go.

I got about 230 good listings for F cameras with the above search string.
Also, click "SLR" on the left-hand refinements.

One potential drawback is that this type of search does eliminate some actual "F" camera listings from people that have spam-listed "F" cameras under bogus listings (like "F6") but that is ok by me. I don't want to purchase from sellers that engage in that type of listing anyway.