Rick on Twitter: "Quick #electronics tip: You can use a p-channel mosfet and a resistor to add reverse polarity protection to a circuit if a diode doesn't work due to it's voltage
power supply - MOSFET in reverse polarity protection - Electrical Engineering Stack Exchange
N Channel Mosfet Reverse Voltage Protection - General Electronics - Arduino Forum
Reverse Polarity Voltage Protection Using P-MOSFET - Electrical Engineering Stack Exchange