Honestly your best option here may be to get one from Amazon. My friend lives overseas, but he is using a us account. So to buy time he has to go to Amazon and buy a us card. If square doesn't let you "cheat the system" by trying to buy it with a us account, that may be your best bet.

To answer your question though, it's just standard that you enter a shipping address. You will be emailed the code though.