seems like Horse Butte would be the place to start. http://www.horsebutteranch.com/index.htm
The University of Maryland sells Wye semen, but I don't see Bannon. https://agresearch.umd.edu/wye/wye-angus/semen-sales
Bannon does have a good pedigree. John Cotton in Volga, SD has a lot of Leonid concentrated cattle and probably could tell you about Bannon. Or try Morgan Hartman at Black Queen Angus.
Thanks so much for the additional information librarian!! I have reached out to the sources you provided and hope to hear back from them. Anybody out there used this bull?