Warehouse Fabrics designed and demonstrates how to create these awesome baby car seat pannier bags with expandable cargo pockets! This is a sewing project that I would be inclined to use a laminated cotton, vinyl, or an oilcloth to make the bags. (I would never use the white fabric pictured because *my* kids would have destroyed them during the first hour.) You can make your own laminated cotton, or you can buy it*. You could also use a heavy canvas to make these handy bags. The cargo pockets are large enough to hold a toy and a sippy cup on each side. Any new mom would love these bags. If the expandable cargo pockets are not quite something you can handle right now, try a simple flat bag construction as done here with a chair tote for the patio.
Oilcloth Wheeled Shopping Bag