Good luck. I
only located something remotely similar to one copy,
but in one unreadable format, in:
ftp.univ-angers.fr/pub2/rfc/rfc/std/std39.txt.gz
This file is 3.3k long, instead of the 187 bytes of the official
STD39.txt
What's unreadable about it? It's an ordinary text file, compressed
with gzip. However, it's not STD39 at all. It's not even related to
it; it's RFC903, which is about RARP (Reverse Address Resolution
Protocol). It looks like the people who run that FTP site have not
only not updated it in ten years, they've accidentally copied their
STD38 file as STD39.
FWIW, I also got unreadable cruft when I used WinZip to extract std39.txt.
Vince