I haven’t found any other sources. It’s probably best to think of this as a hopeful thought for now. Who knows? Maybe some disgruntled secretary will pull it out of storage.
If Ford sent it to the same people, especially Feinstein, it was probably shredded the moment the newer letter was read. They should subpoena Feinstein’s records and whoever else in her office handles them. Maybe her personal Chinese spy overheard something.