"This item is not available for purchase."
I own one of those. They don't work. They also don't make them anymore, though I can't remember why.
It's sometimes possible to get onto wifi. Sometimes, but not always. There are routers that Nintendo products can't access for one reason or another, like some D-Links (which are the ones used in my current residence, unfortunately), and public internet usually requires some sort of confirmation password or something to access it, making it inaccessible to DSes (I've tried connecting to the internet in McDonald's, my local mall, and Panera Bread, as well as a few other places; none of them can connect my DS to the internet, despite advertising their free wifi capabilities). The only times I've been able to access the internet through my DS were when I'd be going to visit friends at my old college and staying in their house, which had a router I could use. That's not the case anymore; I'll probably miss out on the Enigma Stone event, unfortunately.
The best we can hope for is that in the future, wifi events will exist for at least a longer window of time, if not forever (or at least through that generation). Of course, we can also hope for customizable characters or Cyrus and Giovanni to team up and form a super-evil organization, but who knows if any of that will ever happen?