Finding the breeder for you takes time and patience. You may find these websites helpful in your search for your special Doberman.
The DPCA website has a breeder referral list at: DPCA Breeder Referral
You can also peruse Dobequest, an online Doberman database: Dobequest
Other great sites are: DPCA Public Education and DPCA Breeder/Exhibitor Education On both of these DPCA sites you will find a WEALTH of information about Dobermans and how to evaluate a responsible breeder.
Please also consider adopting a Doberman from a reputable rescue. Visit the DPCA rescue site.