I saw a copy of Lomax's Folksongs of North America listed on eBay auctions the other night. I think it was in the history section, not in music books, so it would have been easy to overlook. I'm afraid it's too late now, but the used book sites mentioned earlier in this thread should work for you. Bookfinder only goes 25 books deep, so it may be wise to try the individual sites they list (Bibliocity, Bibliofind, Powell's, ABE, etc.) as well. I've found books listed by, for example, Ray Boas, Bookseller, on his own web site that didn't turn up when I looked for them on Bookfinder.

If you fail to locate a good copy of Lomax, I have several, including one of the paperback editions. I could be tempted to part with one. Reach me via the personal message thingy up there at the top of the page.

Sandy