I'm not sure about the size of the boxes fit your needs or not but I've done something embarassing at NSK where I went in the supermarket with trolley, talk to the staff whether can I buy those used boxes that are empty and I happened to talked to one of the supervisor there (you need to talk to the supervisor in order to buy it since you need their clearance at the counter later) and he ask me to go around the supermarket and collect empty boxes that I want to buy. Then head to counter with the supervisor and ask him to do the magic at the cashier and give you receipt + the price for the boxes. lel.