I have found it very difficult to find unripe (green) tomatoes anywhere in the city, even at the major farmer's markets, like the Ferry building. The only place I have ever found them is one stall at the Alemany Farmers market that fairly regularly has them.
I would prefer to find them in a more central location in the city. Has anyone seem them regularly and dependably at any of the farmer's markets or groceries in SF?
As an aside, I find it humorous that I have to refer to them as "unripe" when asking at the markets, If I say "green" they always point me to the green heirlooms!