I was typing on my phone when I wrote that post above, so let me elaborate, just in case you are serious about this search and want some opinions on how to go about it.
I've been informally tracking T1N Interstate and Parkway re-sales since some time in 2015. Among those advertised nationally on the most common sites such as eBay and RVTrader, I haven't seen more than 20 new listings per year, in total. Going back to about May of 2016, here are the locations where I've seen listings originate (omitting scam listings, which do occur): FL, IL, OH, FL, AZ, AZ, FL, CO, FL, GA, MS, CA, NC, FL, NV, TX, WA, FL, FL, OK, NE, IN, CA, MD, CA, MS. So you can see that there's not much in the way of pattern or geographic concentration.
Of the major national sites, only RVTrader is listing one of these for sale right now (
here).
I don't rigorously keep up with the local and regional dealers whose ads are more limited, as they are more difficult and time-consuming to search. But if you are interested in doing that, here are a few big ones that I recommend:
1. Arbogast in Ohio (big Airstream dealer)
2. Sunshine State RV in Florida (they specialize in Class Bs)
3. PPL in Texas (for the sheer volume of used units that they sell)
Right now, of those three, the only one with an Airstream Class B for sale is Sunshine (
here).
Hope this helps.