When all hope is lost, try your public library. Ask a librarian, and mention John Jacob Niles and John Lomax as editors. Don't overlook the possibility of Inter-library Loan.

As for Nina Simone, she is basically singing an old version with maybe one or two changes of note. And of course, a lot of ornamentation which would be very hard to write down. If you like the song, I think you can enjoy it fine without the ornamentation.