If you haven't found one yet..

If you are looking for a doberman with the protective qualities, I have heard that the United Doberman Club has members that breed specifically for that protective gene that is supposedly sometimes lost down a line of breeding. I don't know a ton about dobermans, but if they were bred for protection, I don't think that trait could ever really be lost. You would know more than I would since you've owned them, I just wanted to throw that name out there just in case. You could always use it for breeder referrals.