You're right to be avoiding Pet Stores and puppy mill set ups. It's also just as important to avoid what are called "Back yard breeders" too. Back yard breeders are hard to weed out because on the surface they seem like they are decent breeders. Unfortunately you're going to get just as many health and temperament issues from them as you would a puppy mill dog.
Sadly, "where can I find a good puppy" is a hard question to answer, because it's not just "Go here!". It's a lot of work and research.
Start by googling Golden Retriever breeders in your area. You can also check out the Golden Retriever Club of America if in the US (https://grca.org/)
When looking into a breeder, there are things you should see on their website, or if not there they should be very open to providing answers to. Things that you need to look for in a responsible breeder are:
*Are their dogs proven in either conformation, sports, or work? Even if you're just looking for a family pet, having a dog from proven lines is important for temperament and health reasons. Being proven means having titles if conformation/sport, or proven to work (hunting, herding, etc).
*How many litters do they have a year/how many litters do they have at once? If they have multiple litters from multiple parents on the ground at the same time, that's a huge red flag. It's hard to devote your time and attention to one litter, let alone more. Are they breeding the female every time she's in heat, or only once a year?
*How old are the parents? Breeding them before they're fully grown (2-3 years old) can be harmful for the mother and babies.
*What health screening do they do? Each breed has unique health concerns that plague the breed. It's extremely important that the parents of the litter be screened for these conditions. According to the GRCA Goldens should be screened for Hip Dysplasia, Elbow Dysplasia, Eye Disease, and Heart Disease. This is also why dogs under 2-3 years of age should NEVER be bred, because you can't test for most of these under the age of 2.
If the breeder comes back with answers saying that they're family pets and don't need to be in shows, they breed multiple times a year or have multiple litters all the time, breed them at a young age, or say the pups are vet checked and healthy, those are all red flags and should be steered away from. I hope this helps guide you in the right direction.
As an aside, I would say to stay clear away from goldendoodles or the like if you're set on a Golden Retriever. The Golden Doodle is a mix between a golden and a poodle, but the results are nowhere near consistent as far as looks, temperament, and grooming needs. You'll get exactly what you're expecting from a well bred golden puppy in those categories.