Try to swap the polarity of the supply!
The 20M resistor simulates the leakage current of the mosfet and the 100k bleed resistor is used to limit the reverse voltage due to the leakage current, can be lower value in real application.
Also please be sure that your PMOS can handle this much gate voltage.
A equivalent circuit can be made out of a NMOS but you would loose common ground.
