Stable dark matter (DM) particles may arise as dark pions from the confinement of dark quarks in a strongly interacting dark sector. Their relic abundance is determined not by annihilations into visible particles but by dark pion number-changing processes within the dark sector. However, this so-called SIMP mechanism faces prohibitive constraints from bounds on DM self-interactions. In this talk I will show that annihilations involving dark vector mesons in the final state dominate over the traditionally studied SIMP process if the dark vector mesons are sufficiently light. As a result, the preferred DM mass scale increases and DM self-interaction bounds can be evaded. At the same time, this scenario predicts visible dark meson decays, which can give rise to striking new signatures at colliders and fixed-target experiments. I will show in particular that Belle-II has excellent sensitivity to the resulting dark shower signals.