I'm not sure what would be the grounds for excommunicating Catholic business owners, or precisely what "refuse to supply a living wage" even means. But I think your options are limited by tying yourself to Capitalism. Catholic teaching and thought really steers us in a different direction, which is to give more workers more of a stake in the means of production and thereby allow them to reap the benefits of their labor beyond a fixed hourly wage. If we can move our society in that direction, which I think is quite possible, then the magnitude of the wage issue - which is really an artifact of Capitalism - will diminish.