Recommended snacks from supermarkets: "Peanut Sable," "Sugar-free Dark Chocolate Hazelnut," "Dark Couverture Chocolate," and four other items.
Here is a list of snacks available at Gyomu Super that I have eaten and enjoyed in person. They are "Peanut Sable," "Sugarless Dark Chocolate 72% Cacao," "Sugarless Dark Chocolate Hazelnut," and "Couverture Chocolate Dark."