One (free) way to practice ethical consumerism is - when indifferent - always to buy a less popular brand or variant of something. This is to counter the winner-takes-most effect seen in the dirichlet distribution of market share. Hence try to buy baba ganoush, not hummus, soda bread not sourdough, Chapel Down not Champagne, etc.
The only person I have ever seen write about this is
@rogerLmartin . But it's quite important.