> In countries where unions do work, that is another door to go search for help.
That assumes your union rep is inclined to help you. In practice (not principle), they have the same incentives as the other managers and HR do in this story. The union rep could decide that the harasser is more important to their union, politically, than you are, and decide not to take action.
Plus, the union can simply terminate your membership as retaliation. For a closed shop, that's equivalent to firing you, but without many of the legal protections that come against wrongful termination.