I am a fan of Abe Books. If you aren’t familiar with it, it can be a great alternative to Amazon, especially if you are looking for something older and don’t care if it’s brand new. I have found you can find everything there and I have bought some old first aid and safety books from the 20’s to use in presentations and as gifts.
Abe Books published a list of some of their most unusual books which I am currently fascinated with. Who would have known there would be entire books on the History of Concrete Roofing Tiles ? or Favorite Flies? or Stray Shopping Carts? Check out the books highlighted here and if you have some time, search around and I bet you’ll find some safety books you just can’t live without.