I take a standard step-down transformer and flip it around to use it as a step-up.
Instead of feeding a AC voltage, as is standard for a transformer, I connect a 9-V DC battery across the lower-turn coil. There is no output voltage across the higher-turn coil, except at the instants when the 9-V battery is connected or disconnected.
The voltmeter seems to suggest a much larger (induced) output voltage upon disconnection. I am not sure if I can trust the >1000 V reading. But I usually make my students (typically about 13) join hands to take the place of the voltmeter. They sure enjoyed the electric shocks when I connected/disconnected the circuit.