A little over a month ago Audible was the first (and only) retailer after Pottermore to carry the official Harry Potter audiobooks, but now they're becoming more widely available.
Barnes & Noble is now carrying the complete set of Harry Potter audiobooks. They have the Americanized edition with Jim Dale as the narrator, and are selling them for $25 to $40 each. That's a slight discount from the prices on Pottermore, but slightly more that the price at Audible.
The audiobooks are being distributed by Findaway, which means that they should eventually be available through other retailers and through subscription services.
My contact at Findaway has confirmed the news, telling me that "Findaway is distributing the Harry Potter digital audiobooks to Barnes & Noble via our AudioEngine platform. They are currently the only partner of ours that has these titles available."
If you want to listen to the audiobooks for free through Scribd, TuneIn, and Playster, you can wait for wider distribution. But if you want to buy a copy, the best deal is still Pottermore, where you download DRM-free MP3 files.
Audible has the better price for individual audiobooks, and the better platform, though.
image by Brian Lane Winfield Moore