Your largest screening list for book purchases is "ADDALL", because it searches the greatest number of booksellers. By the same token you can conduct the most thorough search by using ABE's search mechanism.
Now only members of the ABE membership group of
booksellers is on that list. However there are several thousand from
around the world, and the ABE advanced search, when you master it, is
peerless. Nothing else will produce the results it will produce.
Using it you can hunt by publishers. So: Railway Education Bureau;
International Textbook Company, (this is ICS); McGraw-Hill;Wiley; Theodore Audel; et al - will each produce thousands of technical, industrial, craft, and other titles. Key words like "steam""railroad", "engine", "trolley",and any other word associated with any other subject you are interested in will return countless books. Some will be what you are interested in particularly , however you will note certain book dealers
have concentrations of books in an area you are interested in. Then you can go and specifically browse or search, that dealers stock for books you care about.
I can say flatly that you will beat E-BAY pricing, and deal with a
whole better class of entrepeneurs in most cases. There are also
some such as ZUBAL's, the giant store in Cleveland, that specialize in technical books, or Bennett Feely in Pitsburgh, who specializes in
railway signalling and track materials, where you will pay premium
prices. This is because they pay well to sellers , in order to accrete
the specialized materials they offer. So it is often a matter of buying
from them, or waiting a very long time to achieve what you want at
a lower price.
Good-Luck, Peter