Touge-no-Kamameshi and Daruma Bento
I would recommend Touge-no-Kamameshi and Daruma Bento from Gunma prefecture. They can be purchased at Nagano Shinkansen stations.
They are assortments of traditional Japanese foods in a small ceramic pot (Kamameshi) or Daruma shaped plastic bento box (Daruma Bento). These containers can be reused for cooking hot pot or a piggy bank.