Oh, and there was one more thing I wanted to share with everyone--basically answering my own question here--but I found that for those who are in Japan long-term, or at least have a shipping address in Japan, Amazon.co.jp, Rakuten and (to a lesser extent) Yahoo! Japan Auctions are great places to look for SCANDAL goods, especially if you don't mind used items. They're significantly cheaper than brand new goods, and perhaps most importantly, shipping within Japan is both fast and inexpensive, so overall you can save quite a bit of money.
Bought both Temptation Book SCANDAL and Girls Be Scandalous on Amazon Japan, and I must say I'm extremely happy with both purchases
Book-Off is another place you can find used books, magazines and CDs (online and physical store). However, you have to be really lucky to find a store with SCANDAL books/magazines, and while singles are cheap, albums, even used ones, tend to be a little bit on the pricy side--although I did find some Baby Action CDs being sold for 1290 yen.
Hopefully someone will find this information helpful! Always open to more suggestions and questions~