I had never heard of them, so I looked it upon the web and can't say that I've ever seen any sold around here. That's not to say they're not available, I just haven't seen any and I go to local produce stands all the time.
Fiddleheads? I lived in Danbury, Ct. You can purchase them at: http://www.fiddleheadsfood.coop/ Drive safely! LOL
My husband loves them too,I ordered some canned one's for him once but of course they didn't taste as good as the fresh one's. You can order some here: http://www.upthecountycreations.com/Canned-and-Frozen_c_18.html The type of fern that produces this type of fiddlehead does not grow around here though.
We have bought them at the Harris Teeter stores for the last couple of years. I imagine Whole Foods and Fresh Market may have them. They are only available for a short time. The Kroger on 70 and the one on Six Forks have a lot of interesting produce, they may carry them also.