Luger at Random. Available on Amazon.com and many other places. It's an old book.
www.amoskeagauction.com will sell some Lugers at beginning of June. You may want to take a look at their catalog.. they have typical samples.
www.morphyauctions.com also listed some in June session.
There are many many more auction houses. You may find 88 and P7 there too. Could be very cheap.
www.rockislandauction.com has lots of German pistols for sale in June.