There is
another person looking for this program but there seems to be no answers for now.
I have a 4285A and I would also like the 04285-65002 version for my instrument.
I also tried to look in various programs for
HP9000 but this is a very specific software that is difficult to find among common computer programs.
Too bad, because it would be enough to have the Basic listing to be able to translate everything into Python or another language manageable by modern computers.
I dumped all the instrument's memories, U12-U24 eeprom included, but belonging to a 4285A I don't think they will be useful to you.