If you're hunting for a factory-released purple Nintendo 3DS, you'll come up empty—no standard purple 3DS, 3DS XL, or 2DS was ever sold in Japan or any other region. However, there is a purple-adjacent option that often gets confused: the Purple & Black 3DS XL, which launched in Japan, Europe, and Australia in 2014.
This two-tone model features a deep purple upper shell with a matte black lower half and buttons. It was released as a standard retail SKU (not a limited edition) in the regions above, but notably not in North America. If you're in the US or Canada, this model was never officially sold—you'd need to import.
Your best bets are third-party solutions:
Just remember: any shell swap voids your warranty (long expired anyway) and risks damaging ribbon cables if you're not careful. But for a truly purple 3DS, it's the only way.