As stated above, there are a lot of options. I have an Avenir saddlebag, large, that is expandable. Not sure how much total area, but quite a bit. When it is chilly to cold, I find the need to either put on or take off clothing as the weather changes. With the expandable bag and a small top tube or handlebar bag, I can be out for hours and stay comfortable. Ortlieb makes really nice, but expensive, bags of different varieties. I use light arm/leg warmers, caps, and jackets/vests or jerseys. Not much weight and take up minimum room when compressed. I also, at times, use a small front rack a smallish bag and/or net type bungee cord. I do have a chore/beater bike that has a rear rack that I use for shopping/errands and chores.