With Super Smash Bros. coming out soon, and the 3DS already having other fighting games like Super Street Fighter IV and Dead or Alive Dimensions, this new peripheral coming from the company Cyber Gadget, is probably the closest add-on you'll get to emulating an arcade experience.
The two sides of this peripheral clip on either side of the 3DS XL, and the arcade stick stips on top of the d-pad. That of course will depend on what games will work with it, since the movement has to be tied down to the d-pad for it to work correctly.
Though it does look a little bulky, seeing as how the 3DS doesn't have any arcade like peripherals, this might be the next best thing.
However, the catch is that it's only releasing in Japan this October for 3,000 yen, which is around $30. No word on whether this peripheral is coming to the US, but importing it wouldn't be out of the question.