I have a few methods for finding such things:
1) Ebay obviously, but check the box "completed auctions" on the left-hand side.? That way you will see older auctions as well.? There is also a check box for "worldwide".? You can also visit foreign Ebay sites, such as ebay.com.au (australia), ebay.com.it, ebay.com.de ....etc? Foreign ebay items will not appear on the US site unless they ship to the US.
2) Do a google search such as beginning electronics book images.? Or maybe throw in the word vintage also.? There will be pages and pages of images.? Sometimes you will see an image of the item you are looking for.? And hopefully you can see the author.? This has also worked for me when I was looking for schematics.
3) Different search engines give different results.? Try duckduckgo, yahoo, bing, hotbot, etc.