The Joint Investigation Team (JIT) image shows a "Venturi", which emits propellant gases, like a car exhaust.
Dutch prosecutors want more information from Russia about the Buk, which they say killed 298 people aboard Malaysia Airlines Flight MH17 in July 2014.
The West and Ukraine say Russian-backed rebels fired the Buk missile.
Russia argues that Ukrainian forces downed MH17. The Boeing 777, en route from Amsterdam to Kuala Lumpur, crashed in rebel-held territory.