As much as I like putzing around in used-book shops, I have really had good luck with amazon.com. If a book is outta print they have a used-book network that can often get the volume you want at a good price. takes a while though.
i got a very useful iai paperback from them for about 4 bucks, and a nice coffeetable book on medieval armor.
search their site for sword/knife words and i think you might find something.