Here's is a good search engine for the Craigslist, key in Airstream then click on
Actual Listings (Slow) - This will display actual listings only from searches that return results.
NOTE: Please be patient. This search may take a long time as it has to perform the requested search for each location and return the results. This could take anywhere from 20 seconds to 5 minutes.
Anthony Damata's Global Craigslist Search Engine