Yeah, most of the cheap chargers just have a regulator in there to drop it to 5v, and maybe some diodes and inductors if you're lucky. To actually tell the device to jump to high power mode (500mA) you need some sort of 'smart' IC in there.
You'll probably find branded chargers will have something like that. For example I have my old HTC one - Mini USB tho
- which works ok. I might have to chop it up for my samsung...
I would try a nokia branded one if its not too expensive. FYI the old chargers needed to use a PWM to charge the battery, so make sure you get one that either has a USB slot AND comes with a micro USB cable or has a micro USB cable attached to it.