Welcome to FT!
Anyway, depends on what quality of "boba" you want-there is a national chain, mainly in California but also on east coast, called Lollicup, but I think their artificial powder and other ingredients aren't too good for you. Visit Chinatowns or busy pedestrian areas (such as near colleges) to find such places. Sometimes they can be found in tea places (like in Boston & Cambridge there are a lot) or with smoothie stores.