If you go on the Rootsweb.com site and get an account you can go to the Benjamin surname message board. There is a man named Frank Benjamin who wrote an addendum to the book you mentioned. He said he will do look ups.He said that the Mormon Library has a copy of it so maybe you can borrow it through one of their local genealogy centers/libraries.Maybe it is on microfilm. I haven't tried Ancestry.com to see if they have it on their stories and biographies tab.
There is a book on Benjamins on Google Books that you can download too but it isn't the same one you mentioned.