Hi Andy,
Sorry to hear about your son's diagnosis.
In terms of looking for a miniature schnauzer, you're unlikely to be approached by breeders on the forum. The best places to start talking to reputable breeders is by contacting the breed club secretaries and asking for the breeders list - Miniature Schnauzer Club, Schnauzer Club of GB and the Northern Schnauzer Club. Before doing so, I would write down what you would want from the breeder. For example, as well as being home reared and mum being present at visits, for me, it would be someone that is breeding for a reason other than to make money (for me, that rules out commercial breeders/puppy farmers)! I am buying a Miniature Schnauzer so I would want the breeder to be breeding to type - this usually means they have an invested interest in the breed - they show their dogs, and do all the relevant health tests (parents MAC and eye tests by a BVA eye panelist and litter is eye screened by a BVA eye panelist before they come to you). I expect the breeder to have all their Miniature Schnauzers live in the house and are part of their family, not in kennels. In addition to the above, I'd expect the breeder to offer life long care and support for their puppies - I'm not buying a fridge so I want all the insight I can get from their breeding lines, who best to ask than the breeder?!
Happy to answer any questions you may have about the breed

Good luck with your search