Pololu 9V 0.5A DC-DC Step-Down Voltage Regulator

Pololu has set the standard in compact DC-DC Step-down regulators with clean output, suited perfectly for RC applications, including multirotor and FPV electronics. Even though many devices such as video transmitters and cameras are rated for full battery voltage, they may not be able to handle the spikes from power on, or ESC's. Using a regulator will insure your sensitive electronics get clean and stable voltage and keep them from burning up. Lower voltage can also help your electronics run cooler which can also increase lifespan.

This family of switching voltage regulators can handle voltage up to 36VDC and will provide up to 0.5A of 9VDC power with up to 93% efficiency

These regulators are a great option if you want a flexible system that can run on 3S batteries,

The regulators feature short-circuit/over-current protection, and thermal shutdown helps prevent damage from overheating. The boards do not have reverse-voltage protection.