Use petfinder.com or a "breed rescue" site - if you go to the AKC site, they have a list of rescue organizations by breed here.

My recommendation would be an adult dog because of the time alone he or she would be spending. There are so many dogs out there, of all shapes and sizes, and a shelter or a rescue group will be prepared to tell you if the dog gets along with cats, his or her "staying power" etc.

Good luck and keep us posted!