HMV is probably the only place in Sg where you can get Japanese import CDs/DVDs without going online. But like VidaK said, they charge exorbitant prices for import stuff.
Honestly, get a good friend whom you can trust and has at least a debit card to order it from cdjapan.co.jp for you. Even better, share the shipping by ordering a few different items together. It's much more worth the money.