Just stumbled onto a stainless steel box for sale for $10 online! http://www.zoombabygear.com/item_575/Stainless-Steel-Container.htm My cubic inches to ml says it's around 850, but that's including the domed lid, and approximate. Good for sandwiches and bulky fruit and salads, probably. But cheap! They also have a 12oz stainless steel bottle with nipple cap for babies, but it says a sport cap is available, I guess on request. Also $10. http://www.zoombabygear.com/item_576/Stainless-Steel-Sippy-Cup.htm