I do not know anything about usenet, but these are available on public torrent sites so you may have more success on there?
They are also available on TheStarWarsTrilogy forums, with all you need to know about that in here:
https://originaltrilogy.com/topic/TheStarWarsTrilogy-com-and-invite-codes-to-it-read-the-actual-thread-before-posting/id/76099
ok, I registered for thestarwarstrilogy.com but i can not find were to get 4k77.