Where do you buy shelf-stable plain milk boxes? What brands are there I could look for? I have to send DD's lunch at her new preschool, and she prefers to drink milk at lunch. I send water most days but want to let her have milk now and then. I looked at my local grocery store (HEB), and all they had was Horizon boxes of flavored milk (vanilla and chocolate)....I'm looking for shelf-stable milk boxes that do NOT have added sugar/flavors.