I...believe NTSC chargers have a higher voltage than the PAL chargers, am I correct in saying so? If so, you would need to get a PAL charger for your 3DS I think...As for finding one, just check around on Ebay or Amazon, I'm sure they have them there.
That's not entirely true. A typical european charger which was designed to work at 220/240V will work half as efficient when fed only 110/120V, so keep that in mind. The other way around, using a US charger in Europe will result in burning the fuse the moment it's connected, so let's just say it's not advised to use it.The input voltage shouldn't matter because that's what the charger gets from the power outlet. In Europe the default input voltage is 220-240, but in America it's half of that. The charger more or less takes the input current and converts it to the output current. (in this case, 4,6V and 0,9A) Since the output is the same (Ampere is just as important as Volts!), you shouldn't have any trouble. I don't advise trying to use the PAL charger though, especially because you have a working NTSC one so it's not really necessary anyway.