Hi, I moved from a Samsung S3 to the Moto G. By accident I put the Moto G into the S3 dock and it more or less fitted ,not as well as the S3 but enough to be stable and usable. It did have the occasional issue of making the Moto G re-boot but that may have been some other issue. The chargers we generally the ?10 type that you buy from Amazon in the UK.
If you are in the UK then get yourself down to Poundworld and get one of their generic micro USB charger/docks....for the princely sum of ?1. But it won't work if you have a case/cover that increases the thickness at the base of the phone as the USB connector doesn't stick out quite enough to make the connection.
I tried that one , but did find it very wobbly as you say and I was a tad worried that I'd eventually break the usb connection on the Moto G. The S3 ones gave a quite solid feel as they have support going halfway up the back of the phone. I've yet to find one that works with a cover on , and now that I have fitted the EXCELLENT flip cover , I've gone for a simple generic stand rather than a charger.
At least it appears the phone wouldnt fall off. The one motoclive mentioned seemed as if it would put too much pressure on usb port so I didnt get that one.