I have temperature regulated iron, but always use full power. Regulation is just for preventing overheating of the iron instead of getting at exact desired temp.
Quick solution for fine temp. regulation is not obvious to me, since sensor would have to be placed right on the heater.
Some years ago, I used ordinary diode and a switch to do the trick. When you want the trickle power, just put a diode in series with iron. And when you need 100% use switch to short diode, so the iron gets both halves of the sine. It worked well for me...