Look at this Deluxe Coupon Organizer available on Amazon!  I love my coupon envelope that is always in my purse, but I wish it attached to the cart:

Purse Size Deluxe Coupon Organizer – 24 Cards – Made in the USA, $8.00

• Made of durable colorful material 4-1/2″ x 8″
• 24 – 125#lb index cards
• Comes in many colors & Made in the USA
• Attaches to anywhere on grocery cart
• Also comes with 24 peel and stick categories

We all need more hands!  This saves me from having to hold one more thing!