In Boston, it is available at a number of places:

The best place to go is the tiny Juice Bar located on the second floor of a Chinese shopping complex at 44 Beach Street in Chinatown.

You can also go to May's Cafe (on Glenville Ave in Allston/Brighton) for very good bubble tea (standard milke tea), or you can goto the chains of Lollicup around Harvard Sq and in the Super 88 on Brighton Ave. There are also an Infusions Tea Spa and Cassava Bubble Tea Lounge and some others...