Look for the following:
CD - "In Country: Folk Songs of Americans in the Vietnam War" (Flying Fish, FF70552, 1991) contains 27 songs by various artists.
book - "Singing The Vietnam Blues: Songs of the Air Force in Southeast Asia" by Joseph F. Tuso. Texas A&M University Press, College Station, TX, 1990. ISBN 0-89096-383-5 or 0-89096- 455-6 paperback . This book contains 148 song lyrics.