I would ask the vet if it is a good idea to add another one. All dogs are different, but what you see as a buddy, he may see as an intruder. I would take him out to a dog park or pet supply store and see how he reacts to other dogs. A friend may bring a dog to visit and again, study his reaction. He may be happy to have another dog around, but is safer to test him first before bringing another one in.