Living in Alabama, there isn't much demand for bento gear here. I'd thought I'd share what gear I find at common US chains with everyone via this thread.
First off, I can't live without these  containers from the Dollar Tree. I bought them early December, but they're still on the site (in bulk), so I'd imagine you'd still be able to find them in stores. 10 rectangular or circular near water tight containers for $1--can't beat that. They're tiny (can hold about 3 oz), but that what makes them perfect for bentos. I keep one full of soy sauce in the refrigerator to make it easy to fill those little soy sauce containers, but they can also hold exactly half a yogurt, which is my main use for them. They can fit in the larger section of the Urara bento boxes perfectly, with a little room to put a bite of cheese at one end (see my bento here  ).
If you don't feel like spending $5+shipping for some official bento mayo containers, Walmart has little cosmetic jars in their travel/trial size section (usually found in Pharmacy/Cosmetics). Pack of 2 for $1, and they come in pretty transparent blue/pink/purple. I bought some, but have yet to use them (but I've only made 3 bentos at the time of this post). They seem perfect for putting in a smidgen of ketchup/mayo/ranch/etc.
I've been struggling to find a travel cutlery set that wasn't made for a three-year-old. I found these sporks  that seems perfect. The closest Bass Pro Shop to me, however, is half an hour away, so I think I'll save myself the hour commute and buy this off ebay, but I still thought they were worth pointing out. I'm hoping they're flat and small enough to fit into the top of the Urara boxes <3