I bought the device pictured here from Patona. TipTop.
It charges, is very and that relatively quickly. And is light and handy.
It has no switch and only 1 USB micro-charging cable connection.
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The description mentioned (2 different charging methods) does not apply to this device.
At Digitec or Fotichäschtli you can find a corresponding Pantona charger,
that apparently can do this. Search term "Patona Sony NP-FW50 Dual LCD Charger".
But it is twice as expensive: 45.- or 49.90, depending on the supplier.