For what it's worth, you might look for contractors or plumbers that do a lot of commercial work or new construction. For example, our neighbor has a construction company. The guy is brilliant and creative. He has done amazing work on his own house, and, for a good price, he has done some things to our home, with taste and quality. He is talented enough that he could spend all day every day working on zillion dollar or historical homes in the Hamptons if he could market his services there.
However, his highly-profitable business, because few people can do it as reliably as he, is to renovate existing/open franchises of a certain big chain restaurant. Requires meticulous organization and preparation b/c they can only close the restaurant for, say, 36 hours. In the course of doing those jobs, he installs a lot of wall-hung toilets, albeit usually the commercial flushometer kind.
He recently redid our community beach house and insisted (correctly) on replacing the floor model toilets with in-wall Duravits with the Geberit tank system. Piece of cake for him and his guys because they do that kind of work all the time.
Just a thought. Good luck!!