look at rocky mountain powder horns. Lots of different bags. I have 2 . It is not a book but if you do not want to buy one you will have a good look at several
Madison Grants book of Kentucky Rifles pouches is a great resourse. If I can remember right he has illustrations of pouches dating from the mid 1700's all the way to the 20th century. Not only pouches but horns, powder measures, belt knives, bag knives and patch knives. Probably find it from track of the wolf, dixie et. al. & google search.
There's a book out there called Sketches of Hunting Pouches and Powder Horns by Jim Webb. And don't forget Tim Alberts book Recreating the 18th century Hunting Pouch.
George