I don’t know how many POBs are there but for now here are the sites where you can buy the album:

—VLAST SHOP
—Weverse Shop*
—Hottracks
—Aladin*
—Yes24*
—KTOWN4U*
—Makestar*
—Withmuu
—Knpops
—Gift Kakao
—YG Select*

*previously have a pob