You should be able to get an F3HP for $175-$225 in excellent condition on eBay. Just keep looking
Things to look for:
Make sure the camera serial number starts with 16xxxxx. This way, you avoid earlier models that have the old style exposure lock button. The older lock button has a strong tendency to loosen with use and it pops out and is gone forever.
Make sure the motor drive coupling cover is screwed into the base. If it isn't, there will be a hole in the camera base that lets in lots of light. Not good.
Make sure the original eyepiece (not an eyecup) is on the HP prism. It is rubber-coated and prevents scratches to your eyeglasses.