Hopefully you have time to visit a "real" tobacconist, although they are becoming increasingly rare
L.J.Peretti at Park Sq in Boston: http://www.ljperetti.com/directions-contact
Leavitt & Peirce in Cambridge: 1316 Massachusetts Ave in historic Harvard Square, across from Harvard Yard
Thanks for the recommendations. Staying in JP, but was at Fenway today, and will be again tomorrow, so Peretti might work.