TheSamba.com and GoWesty.com are both good websites for finding VW campers for sale in United States. Both sites provide a wide selection of newer Eurovan and Type-2 Westfalia models as well as older bay-window microbus Westfalia campers.
TheSamba.com is a VW-specific website that has an extensive classified section with ads placed by VW camper owners from around the world, along with a deep selection of parts and other specialty VW models. For U.S. searches, the site provides functions that can narrow the search by state, ZIP code or miles from the original search location.
Another good site specifically for Eurovan and Type-2 Westfalia campers is GoWesty. This site has a good classified section with a number of campers listed. The site also has a wide listing of restored, custom-built Westfalia campers because GoWesty is a Los Osos, California-based VW Bus, Eurovan and Vanagon specialty shop. The restored campers at GoWesty are nice but firmly in the high-end price range.
To find VW campers for sale offline, good places to look are Phoenix, Arizona and central to southern California. These locations have many VW admirers who have spent time and money restoring their campers, and the dry sunny weather keeps these older vehicles in good condition.