Grandma getting another dog?

My grandparents are thinking of getting another dog, but they want to wait for a while and think over the decision. They don't want to replace missy, but they want one because it's a companion. It's a very big decision because they're at the point of retiring and to if they are able to care for a dog. They really love their old dog and they really miss her. They miss how she would be at the front of the door when they would come in the house. If they do want to get another dog, they would get the same size, they don't want a toy dog, because they would want a dog who would be able to protect them because they would feel secure. They were thinkiong of getting another breed, but no to sure what kind of breed they are looking for because it's hard to find a breed like missy. My grandmother has had other dog's as pet before , but it has been a while since she's had a dog when she got missy.