Just Bento

Hmm, the MA area seems to be a bit poor in bento shopping sources, judging from the Japanese food shopping page and the Bento Store Locator on Lunch in a box (which seems a bit out of date, since Porter Exchange / Kotobukiya closed a couple of months ago). And the Korean groceries listed do not usually carry bento boxes. Unless someone can pipe in here, your best bet might be mailorder or a trip down to the NYC area, which has several sources.

There are some stores - Super 88 here in Mass near Boston.

http://www.super88market.com/

I have found some stuff there, mostly ingredients-wise. I havent been to the larger store in Quincy but I hear there are bento things there!

Kam Man in Quincy. The department store has a whole shelf of them.

I know this topic is two years old, but I stumbles across it now.
Ebisuya Japanese Market in Medford MA has a few boxes and accessories. I like this store, it's small, but the staff is friendly, and they get more stuff in each time I visit... this store opened just last year, so it is very new.
H Mart in Burlington MA is also very new, but they have a few bento boxes a well, More accessories and chopsticks too. Try the kitchen section first, the cuter stuff is sold in the front of the store for a lot more money, but there are good boxes for cheaper in the kitchen section with the accessories. If you go, check out the bakery or the food court. YUM!
And say hi to the only non-Asian guys working there (lol). They are friends of mine from school.