Well, I don't think there is a bottle that will not leak. (even if they claim not to leak) All I did for my little one, I would fill the bottle with milk, and then use seran wrap (plastic wrap) and put that over the bottle before putting the lid on. Vualla! When it tips, no milk leakage. And, if you don't want to deal with plastic wrap, just get ziplock bags, put the bottle top in, then put the lid on. But that would cost a whole lot more than plastic wrap.
Hope that is helpful. I was just tired of getting everything wet with milk and being paranoid when my bag tipped.