Breeders have a couple of litters a year and might keep back one puppy. They don't keep back a bunch since it would be difficult to give each one the individual attention and training that is needed in the first year. On occasion, a breeder may find that the puppy they held back last year, or the year before, is not going to work out in their program. Like swamp collie says, this puppy has had a fair amount of training and work put into it before the breeder decides that it would be best to place that puppy in another home. These started dogs are few and far between.
That being said, it does happen. I just placed a 2 year old boy that did not have the "right stuff" for me. While this dog was a wash out for a breeding program, he was incredibly well trained and had 2 JH legs under his belt. After a week or two of bonding his new owner was ready to take him out hunting. My point being is that due to the work put into these dogs they are not cheap. Expect to pay 2 - 4 times what you would for a puppy. Even at this price the breeder is losing money when you consider his or her time put into training this pup.
I would start by looking at the breeders on
Hunting Dogs For Sale - Gun Dog Breeder Classifieds and contacting the 4 or 5 that interest you. These should be ones that do all the clearances and actually campaign their dogs. When you find one or two that you like ask to be put on their list for an older pup or dog. Be prepared to wait but call back every 4 or 5 months and check to see if anything has come up. That phone call lets the breeder know you are serious and prepared to wait for the right dog. I would also keep checking gundogbreeders since I see a started dog for sale on there every few months.
Last thing is that I would be prepared to travel outside of MN to get this dog. Widen your search to the entire Midwest unless you are prepared to wait for some time.