J-List sounds like a fine place to buy it from.
Last year, I subscribed directly from the company that puts out the magazine, but you need to use a Japanese address or mail forwarding service for that. I'm not even sure if they will be offering subscriptions this year.
You can also purchase the magazine from Amazon Japan. The only other place I know of that used to sell it was Akadot Retail
, and they don't seem to have any issues in stock anymore.
I don't think there will be a special edition of the next issue. Occasionally, there are special flyers that come with Yuri Hime
books (if you buy them from the bookstore Tora no Ana, for example), but that's about it. Last year's direct subscription of the magazine came with a special Petit Yuri-Hime 2010
booklet, but I haven't seen anything about whether they'll be doing that again.