Amazon has the Lifecolor Waterproof Diaper Bag Backpack (Orange Pink) for $30 - $9 off with coupon OX6TU4EB (Ends 1/14) = $21 with free shipping on $25+ or with Prime. Features a large main compartment, three insulated bottle pockets, waterproof diaper pocket, two side pockets.
Has excellent Amazon Reviews.
Walmart has the Rockland Melbourne 20" & 28" Spinner Set (Charcoal Gray) for $68 with free shipping. List price: $90. Made of durable lightweight ABS. It features a polycarbonate construction, expandable design, and four 360° wheels.
Walmart has the Ozark Trail Lightweight 40L Hiking Backpack (Gray) for $21 with free in-store pickup or $5.99 shipping to home. List price: $54. It's made with lightweight nylon fabric and has a large U-shape zippered main, and includes a rain cover.