Does he have a car? Naked Fish has steamed lobster on the menu, although I've personally never had it there. That would be the closest seafood restaurant. Captain Marden's in Wellesley does a great version, but a longer distance away.
I know it doesn't get a lot of love here, but I'd consider Summer Shack at Alewife. The steamed lobster is a good as anywhere (IMO) and the pan roasted lobster is very good. Your colleague might have an enjoyable experience.