A neon bulb would require a ballast resistor. You can purchase indicator lights that run on 240, just search around shouldn't be that hard to find. All of the equipment I have at work uses standard mains supplied indicator bulbs, though they typically run off 120 volts. 240 is split phase so the indicator would be run from one of the phases to ground for 120V, same thing with the there phase equipment we use, they only use one phase to power the indicator lights. The current draw is extremely low so it doesn't unbalance the multi phase systems.