the charger works @5V, but I recall that a resistor is needed for the phone to detect the charger as an original charger

I think your best choice is buying one off ebay

2011/3/19 Steve Markgraf <steve@steve-m.de>
Hi,


On 19.03.2011 13:04, Christian Vogel wrote:
What voltage is written on the charger?

230V≈ :-)
... and 3.6V, 600mA

But well, that is not really true. There are 2 versions of the charger, the normal heavy one with transformer, and a light SMPS-one.
The first one delivers 5.94V without load, and the SMPS-version even 6.38V. The SMPS-one states "5.0V 350mA".

You need at least > 4.2V, since that's the voltage the battery is being charged to.

And of course the datasheet of the used charging regulator, Intersil ISL6292C states:

> Supply Voltage, VIN . . . 4.3V to 6.5V

Regards,
Steve