I acquired an inexpensive, insulated "trunk bag" several years ago, brand name "Avenir". It's not a Yeti cooler by any means, but it has an expanding top so I can get those bulky items inside. But I also carry sandwich thins, peanut butter, Spam singles foil packs, tiny cans of veggie baked beans, instant grits and cookware/stove, a package of bagels squeezed down to sandwich thin size, fig newtons, ramen noodle soup, trail mix of dried fruit and nuts. An occasional bag of powdered donuts or Cheetos. I don't believe in going hungry. Put the non perishables in a pannier, and the beer in the insulated bag.