Gothic Lolita Bibles
You can find Gothic Lolita Bible volumes on Amazon Japan. If they are still in stock from Amazon directly, you can get them shipped internationally without a shopping service. If they are second hand, you usually will need a shopping service. FromJapan will do it, but the shipping is painful. I like Tenshi Shop.
Gothic Lolita Bible Search on Amazon Japan
Like with the GLB, you can find some issues of Kera on Amazon Japan, specifically the more recent ones.
Yahoo Japan Auctions is also a good place to look. Check the Teen/Street magazine section. Again, it’s easier to find more recent issues.
Gothic Lolita & Punk Brand Book
For catalogs, try mercari, yahoo japan auctions, fril… anywhere people sell used clothing and use the term カタログ.