If you visit an Asian country, you can probably find this at many cosmetic stores. The alternative would be to purchase online through Amazon or Ebay. I would be careful and do research before purchasing online though. Many sellers sell fake items.
Ebay has the lowest price, but make sure to the rating of the seller as well. I have purchased korean makeup from the following sellers before, they all have legit products: F2plus1, iamlove-shop, ideaseller_kr, sing-sing-girl, rubyrubyshop.
Or amazon! that's where i got mine! :) i just typed it Asian bb cream and there it was! Look at the sellers though try to get one from the U.S because if u get one coming from Korea or japan it takes longer to arrive! good luck!:)
Amazon.com and Ebay are your best bets to get this, although you do need to be careful not to get ripped off. There's been recent issues with fake Skin79 creams being sent out, but most of that has died off now. Also, if you live in an area with a thriving chinatown you might be able to just straight up buy this at a drugstore/supermarket.