Shirdi Sai Sansthan have following books published on sale with them. Below is the list and their price.
For your Sai books (if you are in India ) requirement please contact:
http://www.shrisaibabasansthan.org/main_English/sansthan/publications.asp and follow necessary instructions. Or you can arrange from somebody who is visiting Shirdi to personally collect from their office.
If you are outside India , you can try at www.saibaba.org or similar other websites. They deal in Sai books over internet.