The price on the book in 1980 was $9.95 USD, shipping was $3.90 USD. I ordered my copy through a local book store, it came from a publishing company in Dublin.
Try searching one of these book sites for a copy in your price range: I use abebooks the most, I have accounts with several of their dealers and an open list for flag books, or military history with flag info.
Good hunting & Happy Trails!
Tom Martin
www.Confederate-flags.org