According to him, it is hard to generate positive voltage with the charge pump and charge booster and also to use NMOS brings additional driving circuit which costs some money, That's why I was looking for PMOS. But as you said, It is really hard to find Vgs above 30V and in the most of the applications, designers are using NMosfet.You didn't say anything wrong. Why is your supervisor wanting you to use PMOS?
But I will check this booster thing tomorrow morning and I will do my design with the NMOS. If I can make the circuit work in the real, I don't think he will complain for that.