I see them occasionally at our local specialty farmstand. Fancy enough place that people drive the 15ish miles out from Boston to get, well whatever. Decent prices on the produce they grow themselves so that's pretty much what I get there.
My wife and I used to live in a house that had a huge mulberry tree in the front yard. Fruit way too high to harvest w/o a 20' ladder. One year the landlord had the yard fertilized and we got a bumper crop from just spreading an old sheet under the tree in the AM. Mulberries are really good - like a blackberry that's a bit longer and sweeter - with less seeds.