Lots of places sell blades for rotary cutters. Try Tractor supply or Agri-supply they carry several styles. Most all blades I have seen are the same bolt attachment size, just need length and width to match what you have. First of all, are you sure you need blades. Maybe you just need to sharpen what is on it. As for bearings, Timken makes bearings for lots of things and can likely match what you may need for whatever you are in need of if you have the inner and outer race so they can mike it for exact size or the inner race usually has a bearing number that can be matched up.
$350 would be a good counter offer to start negotiating with and the fact that they are no longer made, would be a good cost lowering advantage for you to pursue.