You can’t buy it in stores yet, but it should be released really soon.
You can buy the region 0 version at Discount Anime DVD. (http://www.discountanimedvd.com/detail.asp?dvdno=11993)
Just go buy the DVD. www.ebay.com has anything you can think of.
The best thing to do before you buy, is to read the seller’s feedback profile. It he/she has any negative feedbacks, read it, and you’ll see why.
I’ve boughten at least 20 things on ebay now, and always received the items. No one has ever cheated me.
If that happens to you, read the feedback profile first.