Hey guys, so, I went to my brother's house today and unfortunately I left my 3DS charger there and that's two hours away. Anyway, years ago when I had a DS Lite I got a used one without a charger and noticed that the charging port looks very similar to a normal mini USB 2.0 cable.
So I just decided to get experimental and see if I could just throw one in, and with a little force, it actually worked! It was my DS Lite's charger for years until it got stolen. Now I have a New 3DS and, like I said, I don't have its charger with me right now, so again, I got experimental.
I don't know how much this will help you guys out, if you already knew or whatever, but it did help me out a lot so that's why I'm sharing it now.
Images are big so I just threw them inside of a spoiler tag ^^.
So....With the first cable.
And then with the second..
One thing I forgot to show: The USB cable does fit all the way in the slot, I just couldn't show that with one hand as it does still require some force to put it in.
Please note I'm not responsible for the murder of your system if you attempt this and wind up breaking your console somehow. >.>
So I just decided to get experimental and see if I could just throw one in, and with a little force, it actually worked! It was my DS Lite's charger for years until it got stolen. Now I have a New 3DS and, like I said, I don't have its charger with me right now, so again, I got experimental.
I don't know how much this will help you guys out, if you already knew or whatever, but it did help me out a lot so that's why I'm sharing it now.
Images are big so I just threw them inside of a spoiler tag ^^.
So the materials are:
Two different mini USB 2.0 cables just to see if they both will work, my ANKER portable battery, and of course, my basically dead 3DS.

Two different mini USB 2.0 cables just to see if they both will work, my ANKER portable battery, and of course, my basically dead 3DS.
So....With the first cable.
And then with the second..
As you can see, they both work! It may have taken a little force, but it does work. As far as I can tell, there has been no damage done to either product. The USB cable has retained it's shape:
and the 3DS's charger port is fine:

and the 3DS's charger port is fine:

One thing I forgot to show: The USB cable does fit all the way in the slot, I just couldn't show that with one hand as it does still require some force to put it in.

Please note I'm not responsible for the murder of your system if you attempt this and wind up breaking your console somehow. >.>