I have posted links to chapters 7, 8, and 9 of Sasama Yohihiko's 1981 book "Nihon no katchu bugu jiten" (An Illustrated Encyclopedia of Japanes Arms and Armor), this translation was generously given for free by an secret donor. There is a lot of very valuable information on Japanese armor in these chapters which have never been available in English before.
Chapter 7
https://drive.google.com/file/d/0B3j...w?pref=2&pli=1
Chapter 8
https://drive.google.com/file/d/0B3j...w?pref=2&pli=1
Chapter 9
https://drive.google.com/file/d/0B3j...w?pref=2&pli=1