You absolutely can find older dogs from breeders! The only thing is you might be in for a wait. Sometimes when a breeder is looking at prospects to keep from a litter, they'll hold on to a couple dogs to see which one turns into more what they're looking for. Then, once they've made a decision, there's an older pup/adolescent dog that is absolutely wonderful for a pet, or even for sport, but for one reason or another just isn't quality enough to breed.
The other thing you may come across is a dog that was returned to the breeder and looking to be rehomed. It could be that the living situation of the owner changed, they were having some sort of issue with training that they couldn't handle, or it could be a washed out sport/working dog. The reasons a dog could be returned our endless, but just like with getting a rescue from a shelter, they aren't all, "The dog wanted to murder my family," reasons, haha! Like you said, if nothing else, the breeder will have a great sense of the dog's personality, and ideally any issues that you may need to work on.
If I were in your boat, I'd look around the area you're willing to travel for ALL the breeders that fit what I felt was ethical breeding. Talk to them, get to know them and let them get to know you. Let them know you're looking around for an older dog, and what you're willing to work with. Then you have a wide net cast so if a dog DOES wind up needing to be rehomed, you can find out and see if the dog is a right fit.
Just like with a breed specific rescue, though, you might have a long wait. But if you're determined, I don't doubt that you could do it!