He's not super easy to find, but it's across the street from the Aladdin bread factory (and their lovely new shop, Baked In Brooklyn), and lately they've had a sign out. The going rate is $4.99 a lb, or 3 1.5 lb lobsters for $20. Even with the lobster glut, that is a deal! And you can go inside and pick out the ones you want. There's just tubs and tubs of them, clacking around on those insectoid little legs of theirs.
In fact, if you're in the mood for a lobster roll, you should pop into the bakery, get a good iced coffee and pick up one of their bags of fresh rolls for $1. You are going to have the cheapest, best lobster roll in town! Don't say I never did anything for you. Believe you me I thought long and hard before divulging my lobster secret, but you guys are cool. Right?