Swapping the back plate which has the serials then returning is illegal but many people do it that's what I was getting at... Find a retail store that has old stock buy it and return it with the back swapped, that's if you country allows open box returns which here in Canada they do. Most people in usa/canada to to EBGames/GameStop because they are to dumb to check for the serial in other places thus easily able to scam them by either swapping the board or if the housing is in condition just swap the back and return. I know somone who found a launch 2ds at a big box retail store recently and he did exactly this.
There have been Atleast one case where nintendo figured out somone switched the back plates and did a return, their console was apparently banned and lost all their digital games, not sure if this story is true but saw it somewhere on gba temp, but many people do this so its relatively safe imo.