Check on Ebay for M5R2 or Mazda/Bronco rebuild kits. I saw a kit on there that had all the solid brass synchros, bearings, gaskets, and oil slinger, etc... I'm not sure what will fit and what won't, but for $200 you might be able to get a lot of bearings, gaskets, etc... for cheap. Not 100% sure if the synchros for 1-4 fit, but they looked similar in the pics. Those alone are $80-$90.
Micah