Google Giant Airedale, he still raises normal size working dogs and the larger variety. I have no idea where to find a working Ridgeback.
I put out the word to other hunters and E mailed a bunch of Veterinarians. Many of the Vets have a relationship with breeders and may be able to point you in a direction.
Over the years I've picked up a lot of discards, dogs either scheduled to be put down for temperament or whatever. Spend an hour or so with the dog, show them a few different pelts or pigs ears, watch them and try to spot the issue with the last owner and decide whether it is correctable or not. Basic prey drive, how they react to your command voice and other factors. Try to spot their dominant traits, some is physical build (is it built for speed), eye dominant or nose dominant. The only up side to pure breed dogs is you kind of know what to expect in a broad sort of way, but some of the best dogs I have had were Mixes, you have to be sharp enough to spot their talents.