Sir or Ma'am,
I have found the National Tribune to be very hard to find, in part or complete. The most complete collection that I have located is at the U.S. Army Military History Institute (USAMHI), Army Heritage and Education Center, Carlisle Barracks, PA. The collection is on microfilm. I did some research with it in September 2004. Currently, I know of no digital collection in existence.
Respectfully,
Gerald D. Hodge, Jr.
War Between the States Historian
Historian: 39th Georgia Volunteer Infantry Regiment
http://39thgavolinfrgt.homestead.com/39thHomepage.html