Plenty of hobby breeders that are passionate about parrots have multiple breeding species. I spent ages looking around. I'll tell you about the breeder I settled on, because I liked how they ran their aviaries (Almost all the birds were pets, even when breeders) and I found them pleasant to deal with. In fact, I am still good friends with them! They are great people. I think you will be looking for similar traits in a breeder wherever you look for your bird, so it might be helpful.
My breeder has ekkies (two breeding pairs) suns (two breeding pairs) and princess parrots (An aviary of them)... All of these, bar one pair of suns they recently got, and one pair of princesses, are hand raised pets, that also occasionally allowed to have a clutch. They also do buy and trade young birds with another breeder in the area to raise and sell occasionally. Alex, my jenday was one of these. As a result I did not get to see his parents, though I was given photos of them, and the other breeders info, in case I wanted to chase them up and see them before I bought Alex.
When I went to look, in addition to their adult birds (which are their pets. They have avairys outside for each bonded pair, but the birds spend more time inside then out!) their were 3 Jendays (one of which became mine!) 4 ekkie chicks, 3 princesses and some GCC chicks. In addition their was one young adult male ekkie for sale (the bird I was originally going to look at actually!). All the ekkies and princesses were bred by them, and the conures from the other breeder they have an arrangement with. All in all there were some 14 birds being hand fed, all by two people! They usually don't have this many, but the lady was injured at work, and now hand raising (not only her own chicks, but also other peoples chicks, currently she is doing budgies for someone) is pretty much a full time job for her that she can work from home.
All the chicks were well so******ed, and spent more time out of their cages then in once out of the brooders and hot boxes. They were constantly surrounded by people and interacted with. None were sickly looking (Besides one chick who hatched deformed and was under veterinary care) and the premises was clean. The breeders were open and honest with me about all things (Including when I asked about the sickly looking chick), and any questions were promptly answered. Keep in mind I was here to look at an adult ekkie to begin with, and ended up falling in love with a tiny pink Jenday who had no feathers! I really got lucky. Great bird, great breeder.
I think you should look for a clean premises with people who genuinely love their birds. A good indication of this, in my case, what that the breeders were also pets, and handled regularly. In fact, they were more then happy to demonstrate and let me handle their breeder birds. I knew instantly that these birds were much loved and cared for. Look for healthy, happy birds who are at ease. Ask questions, and if the breeder is open and honest that is always a good sign. And go with your gut instinct. If you don't like a place, you don't like it. That also goes for picking your buddy out, if you and a bird just seem to click, or a bird chooses you (My little guy did, and I used to think that was crazy bird people talk until I got to have that experience) roll with it!
