Michael,
Portland is a desert for C&R oriented gun shops. Anything you find here will be strictly incidental.
However, Portland has a monthly major gun show at the Portland Expo Center, which happens to be this weekend
http://wesknodelgunshows.com/pages/EXPO.html. There is always a smattering of C&R and antiques, and there will be a couple of Luger-oriented tables.
--Dwight