Any USB socket car charger should work fine.
I have charged mine this way a few times, no issues.
All USB based Car chargers output 5 volts and usually have a variable mA setting inside to regulate whatever the
device needs.
Look on the back of the car charger, it should say something like:
Input: 12-24VDC (car battery)
Output: 5.0VDC - 900mA Max
Hope that helps.