I love the Verti-Grip Professional Knife from caregiverproducts.com. The Verti-Grip knife is held vertically so my whole arm can press down as I rock the blade side-to-side. The rocker knife shown above is held horizontally so I create downwards pressure only with my index finger.
The VertiGrip's sharp blade cuts though steak and pork chops. It is only six inches long so it fits completely inside my purse. It has a protective cover that slides off easily so I put the VertiGrip in a small zip-lock bag to protect the inside of my purse. The Verti-Grip costs $17.95 + S&H, but I think it is worth it.