I have found these books to be most informative about George W. "Bud" Wigginton and his Civil War exploits:
--Joanne Chiles Eakin & Donald R. Hale, "Branded As Rebels," Independence, MO: Wee Print, 1993, p. 466 (also contains data about his origins and family);
--O.S. Barton, "Three Years With Quantrill: A True Story told by His Scout Johh McCorkle," Armstrong, MO: "Armstrong Herald" Print, 1914, reprinted in Norman, OK: Univ. of OK Press, 1992 (John McCorkle was an intimate of George Wigginton--and I think a cousin-- and mentioned him often in his memoir);
--Donald R. Hale, "We Rode With Quantrill," Clinton, MO: The Printery, 1974 (The Printery is defunct, and I fear this book is out of print. Hale has mastered the biographies of most of Quantrill's men).
Some of these books are still available for purchase, or you could view them from your local library via inter-library loan. Wigginton is mentioned in a number of other books, but I recommend you start with these to give direction for your further research.