From what I understand, most of Buchheim's work has never been translated into English or released for publication in English-speaking markets. So if you're trying to find something for sale in the US you may be hard pressed to locate a seller, even online.
At Amazon.com, almost everything that comes up in a search is only available through third-party sellers, and most of those seem to have used copies only. I got U-Boat War that way (used library copy) and I'm happy with it.
I've searched for things at Amazon.de but unfortunately the German site never lets me actually buy anything.
