A while back someone posted that Kam Man Market in Quincy, Massachusetts was a good source of bento boxes and gear and they were so right!
Kam Man has a market and separate Asian goods department store that has an entire section of bento. The boxes are inexpensive too: most are $1.99 or $2.99. There is also a good selection of tools and accessories. I found a wiener cutter, picks, oval food cups made from foil, packs of green plastic sushi dividers, bento size chopsticks, sauce bottles, bands and bento forks. In the cookware section a tamagoyaki pan can be had for $9.99. There is an entire floor-to-ceiling aisle of rice cookers. The house wares section has beautiful and inexpensive Asian dinnerware in every style. The only downside is that the store is a bit of a jumble and many of the bento boxes have been removed from their packaging so be sure you don't buy a box that has been pilfered. I wish I had gone to Kam Man before I spent $15 on a box shipped from Hong Kong! The same box at Kam Man would be $5.00.
The supermarket is pretty big and all of the major Asian cuisines are represented (they are a bit sparse on Indian though.) Their Japanese items include a good selection of basic pantry items like ponzu, Japanese brands of soy sauce, bonito flakes, nori, furikake, goma shio and togarashi. It's not as extensive as the late, great Kotobukiya but still much better (and cheaper) than what you'll find in a regular American supermarket. The Kam Man supermarket is also cleaner and better organized than Super 88 in Boston.
Both stores are in a mall that includes an Asian bank, travel agencies and fun boutiques. My daughters always want Bubble Tea when we go there. The parking lot is a mad house and Asian families from all over the Boston area shop there so it’s a busy place.
It’s a very fun place to shop.