I just picked "Bonnie" up on amazon for $18.00 shipped.I am not sure, maybe it's out of print and not available, it is one that I don't have and is a special book. One thing is sure try finding "Bonnie, The development history of the triumph Bonneville” 2nd edition by JR Nelson and see what you'll pay. And that is the Bonneville Bible; it has every change and lists from which number on it changed etc. As maybe the case with the other book I am not sure.
I bought a book from Gaylin not that long ago. I can't remember his eBay handle either. If I run across it I will post it. He actually buys copies of his own book if they go cheap; apparently he has a list of people who want copies.
Bushy, I think I can do better on describing the differences between Bacon's and Gaylin's books. Bacon's book is much more focused on the actual mechanics of restoration; Gaylins book on the 650s documents the changes over time, focusing on getting everything factory correct for model and year.