How hard is it to make an USB-powered toothbrush charger/power supply?
for giggles I measured my Braun Type 3757 120V 60Hz on my RLC meter and it gave me the following readings on the AC plug.

@1kHz L= 95.37 H, Rs=92kΩ Rp=O.L. Cs = 267pF Rs=92kΩ 

The Rs changed from 72 kΩ and ~100H before I powered it above, so remanence may have affected the readings.

But at 120Hz it gave ambiguous large readings.

So I knew it didn't operate at 60Hz.

Then I scoped the magnetic field with a probe at 27us distorted cycle or 37kHz.

It is rated at 0.9W, so you will need to step up the voltage and use around 200mA RMS to match performance.  Flyback operation will not work with existing coil here due to the high value of H, but you might be able to make an auto transformer out of it with additional windings as primary and modify or bypass the internal switcher.

Hope this helps you.