I am sorry to hear about the lost of your cat .
If you do get another cat ,it might be best to get a kitten . I had a dog and got a kitten and the kitten was too young to know that dogs and cats do not always get along . So the kitten had no fear of my dog and took to her right away as his adopted 'mother' and tried to nurse on her. I think only you know what is best or your dog. Is there any way you can be a foster mom to a kitten that you would want to adopt if your dog got along with the kitten?