Like said above, first step is contacting the breeder.
Second, if breeder is not willing or able to assist, is a Dobe specific breed rescue.
If you strike out with Doberman rescue, look for a well established bully breed ("pit bull") rescue. While the breeds are quite different in type, most bully breed rescues end up with Dobermans and Rotties due to being familiar with landlord and insurance requirements for such breeds and they generally know how to do their verifications that a breed is allowed in an area or allowed by a landlord.
If you are able to keep the dog until a new home can be found (again, that is if breeder cannot take the dog back) then ask for a "courtesy listing"
The rescue can post the dog to petfinder and their own facebook/website, they can field inquiries for you, vet the applicant and they can handle the adoption paperwork. The key is they will not be taking the dog into their foster network and they will not be reaponsible for any expenses in the meantime.