A tote bag is the perfect workweek and weekend carryall. Totes are designed with plenty of room for your essentials - exactly what you need on long days in the city.
If you're a thrifty shopper, your best bet is this Muveil Tote Bag. It's a popular product, while not very costly. Another strong contender for your wardrobe is this Neiman Marcus Tote Bag. While the price of this item is competitive, it will certainly attract a lot of attention.