Mains powered NMOS 100KHz switch with push-pull MOSFET driver
IRF701 requires 10V gate drive, so you'll need a 10-12V power supply. You can use any old 12V wall wart for this.
With a supply capable of a bit more current than a capacitor dropper you can use a NE555 which should have enough output current to drive the FET. Or you could use a MOSFET driver like MCP1401, but the input takes only 5V.