In print, just in my limited collection (limited mostly to the cheap stuff), Back Up and Push appears in:

The Craig Duncan Master Fiddle Solo Collection, Mel Bay Publications, ISBN 0-7866-3387-5

The Fiddler's Fakebook, D. Brady/Oak. Melody Line w/ Chords Only

Mel Bay's Complete Jethro Burns Mandolin Book, Mel Bay Publications, 1993, ISBN 1-56222-663-0

Anthology Of Mandolin Music, Bud Orr, Mel Bay MB93952,

I'm not advocating that you run out and buy a book, but these all are (or have been) popular enough that one of your friends has a copy of at least one of them. (Almost a certainty.) With the variability of older songs in print, you might want to take a look at more than one version before picking the one you want to use.

If you can't find it more easily elsewhere, PM an email addy and I can probably find my books to scan one or more, but I can't promise a really prompt response at the moment.

John