transformerless low-current power supply design
If the power dissipated by the dropper resistor is too high, consider replacing it with a capacitor.  Wikipedia link.  The capacitor needs to be chosen so that its impedance matches the resistor you would have used.  Place a reasonably high value resistor (a few hundred kilohms) in parallel with the capacitor to discharge it when the supply is disconnected.  The capacitor needs to be rated for the full mains voltage.