For reference, US Navy uses mil-spec breakers exclusively. Really nice strong ones, the kind that won't trip just because the case is hit with a sledgehammer (or the ship by a torpedo, which has much the same effect). They still won't work underwater, but that's OK because the panels are watertight.
Anyhow, small sizes are typically acquisitioned in single-phase units, which are all retrofitted using field-installed 2 or 3-handle yokes. Not saying this is necessarily allowed by UL, but DoD is a widely recongized listing agent, too, and it clearly works just fine for the DoD.
