I’m a longtime fan of Japanese AV too, and can help out with this.
There’s a Japanese website called SquarePlus that sells legitimate Japanese AV dvds and other goods. Not only is their website in English and easy to navigate, they’ll also make special orders for you if you want titles that aren’t on their website. I’ve ordered from them three times in the past for old, hard-to-find titles I couldn’t get elsewhere, and they came through for me quickly.
The only downside is that they only use EMS shipping for sending goods to the US, which is kinda expensive at $15.00 for a dvd or two. But it’s fast, and you get order tracking as well.
Their URL is http://www.squareplus.net/index.aspx and you can find their special order page among the others at the top. Good luck!
P.S. You can find a list of some of Mai Haruna’s videos at the X City paysite. You won’t be able to look at pictures or download the videos unless you’re a member, but you should be able to view title and item code information, which will be of help to you when making special orders.