
Have a look at the breeders section here and then chat to them Make sure they understand what you are looking for and that their dogs have the necessary health tetsts.
Also going to dog shows can be useful . To find those look through fosse data website .Also ring one of the gsd clubs/ associations.
Protection work is very different to competitive obedience so be careful who you speak to and what they are suggesting. Working lines are often have a much higher drive and you need to consider if that's suitable for you situation. Most shepherds are going to good for obedience