Use a bag such as this one instead of buying new bags every time. If you prefer black bags, then this should you just fine.
From Freemans
Radley London Pocket Essentials Black Responsible Large Ziptop Tote Bag
John Lewis & Partners
Radley Pocket Essentials Responsible Large Zip Top Tote Bag
Radley
Radley London Women's Recycled Materials Pocket Essentials Responsible Large Ziptop Tote Bag - Black Large