Preorder for a June 16th release is up on Amazon. A bit pricey but this is the limited edition import.
http://www.amazon.com/Babymetal/dp/B00U2E8LE6/ref=sr_1_1_twi_2_lp_?s=music&ie=UTF8&qid=1428634211&sr=1-1&keywords=babymetal
I'm hoping there will be much cheaper U.S. version as BabyMetal has just signed a US distribution deal with RAL/Sony .