Looking for a lined backpack cooler that actually doesn’t leak. All I want is to be able to carry three-four bottles and throw in an ice pack or something.
Try a “regular” sort of backpack, then get some aluminized bubble wrap sort of insulation (you may have to get a big 4 foot wide roll at Home Depot, or else e-mail me and I’ll send you some! 
I’ve got a lot extra). Cut a piece for the bottom of the backpack, and a piece to wrap around the sides and cover the top of the bottles. Then use one or two of those gel-filled “freezer” blocks that they sell in supermarkets to keep everything cold. They don’t leak, so that eliminates that problem! Four bottles should fit wth no problem.
Can I go camping with you?