"Turns out that Plus-X is gone because the one particular machine that coated it broke, and it couldn't be repaired any more, same as Efke"

I call BS on this. Kodak shifted all of its film making to one plant in 2002 that could make all of the films under one roof, just changing the emulsions for the master rolls to be cut. One Kodak machine 'wearing out' for Plus-X? Ha.
Perhaps you got the previous version mixed up, that version of Plus-X pre 2002 had the distinctive blueish film base.