No Nightfall buddy key for online purchase?

I may just be blind, but I haven't found a place to get this key anywhere. I bought Nightfall through the in-game store, and now I have a friend who I'm trying to convince to buy Nightfall, but this supposed buddy key that one apparently gets when purchasing Nightfall doesn't seem to exist. Is this for the boxed version only, or am I just not looking hard enough?

I think it's for the boxed version only. But there are other ways to get buddy keys. Try the buddy Key Request sticky on this forum.