If you haven't tried start with the Fish Finder
I'd also recommend if a place is listed as having it ask them, most places put it behind the counter.
You can also email your distributor for Dogfish, that's found here
Good luck finding it, took us some time, and it isn't cheap. We're currently setting up a vertical tasting of 120 if I can get my stupid family on the same page we have like 7 bottles which would give us a healthy sample, I was thinking of doing every 2 years but even at 1year increments it should be interesting.