Go to AbeBooks. They can run down anything.
AbeBooks LinkA friend routed me there, and I've been reading a ton of really old stuff on our early explorers and hunters since.
+1 on AbeBooks
I've had great luck with them.
They are not a bookstore as such --
they connect to THOUSANDS of booksellers around the world! Yep, thousands, and they are better at finding really obscure books than Amazon.
I have used their "Advanced Search" to find the correct details about a book I had only a vague description of. They didn't have it, but at that point there was a way to "set an alert" -- and get an email when one of their thousands of bookstores found a copy of the book.
You can specify a particular edition, what range of conditions you would accept, paperback or hardcover, etc.
If it is a bookstore in, say, Morocco, that finds your book and not in your own country, you will often have a chance to specify fast (& expensive) shipping or slow & cheaper shipping.
In one case, I think it took nearly a year for them to get a particular book I wanted (it was from a
very small press run of a
very specialized scientific book), but they WILL find a copy eventually!
John