The lid of the lunch box, which is a problem if the contents spill, is fixed cutely and firmly ♪ I found a goods called "Silicon Leaf Lunch Belt" at the 100-yen shop Ceria.
Lunch belt made of silicone rubber (band for lunch box). The length is about 30 cm, and it can be fixed by passing the leaf part through the hole on the opposite side. The standard lunch box is 10 cm wide and 8 cm high. Depending on the size and shape of the bento box, it may wobble a little after it is stopped, but I was able to feel a sense of stability.
The "Silicon Leaf Lunch Belt" is convenient because it can be used not only as a lunch belt but also as a bag for sweets. Why don't you make use of it at events such as regular lunch boxes and picnics? The price is, of course, 108 yen (tax included).