I had similar requirements to yours. I am a female who does a lot of running on the outskirts of town which are relatively uninhabited, but still have vehicular traffic. I feel so much more comfortable now that I have a GSD to run with.
There are a lot of experienced people on this forum who will hopefully chime in regarding lines and breeders who are much more knowledgeable than I am. I adopted my girl at 10 months old. She had come from a family situation with kids ages 4-7, was already house broke, potty trained, and started on basic obedience, and was already old enough where I felt comfortable taking her with me on runs. As an added bonus she was already exposed and used to horses and other livestock.
So, you may want to also consider older puppies/young adults. Whether if it is from a situation like mine or occassionally breeders have older puppies available as well.
Good luck in your search!