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It's a pretty standard accessory, they should have them in store.

EDIT:

Never mind, I was thinking of a different adapter.

Though it's listed as shipping within 24hrs on Apples site. So it can't be that hard to find in store, somewhere.
 
Call them.

I've never understood why people ask these kinds of questions in a forum, as if we know the inventory of the OP's local store. It's much faster to simply call the store and ask, rather than post here and never be sure if the answer is accurate.
 
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