Colin is assuming you're referring to _his_ solution.
But, within that context, he is correct. So, how about a 12V Zener between the 24V signal and the input of the gate [cathode facing toward the 24V signal], with an appropriately valued resistor from the gate input to ground. The value of this resistor will be determined by the driving capability of whatever is supplying the 24V signal and will be limited by both the zener knee current, and the max continuous wattage of the zener.
In this application, though, the conditions should be consistent enough that the zener could effectively be biased at just above the knee current (taking into consideration temperature variation, component tolerances, the amount of stability in that 24 volts (did I forget anything [Colin]?) )
BTW: An 8V zener would suffice, since the supply voltage on the gate will need to be at or above 16V (depending on the output load) anyway, so up to 16V can be applied to the gate (again assuming Colin's solution).