When I read your post, it reminded me of the year we were all jungled up on our way to retreat one February. It was snowing and slushy, and we HAD to stop at JoAnn's before we got to the town where retreat was. We opened up the back of the SUV (which was packed like a clown car), and out fell my bag with all my notions! After freezing my fingers sifting through slush to retrieve them all, I went inside and found a solution. There was a bag for sale that almost looked like a book that zippered. There were several zippered "pages" inside. It fit all my stuff, and I've carried it ever since. I've not seen it again for sale, but this is a link to a pattern that's close:
http://www.byannie.com/shop/product/hold-everything/