Apparently Gamestop and GreenManGaming have copies.

heartless

So if you want to pre-purchase but can't anymore, it seems like those sites still have keys.

Link to post on Reddit.

Edit: I have no way of testing it myself, short of buying another copy but people are reporting that it works.

Lusts

Don't pre-purchase/order at Gamestop website. You will not get the pre-order bonus key if you do. You actually HAVE to go into store and pre-purchase/order and make sure the key is printed on the recept. They have been having problems with handing out codes and 80% of the time, Gamestop doesn't even print the codes on the recept. DO NOT order online at gamestop, go into the store and actually make sure they print it out. I had to demand it when I got my copy on Monday. Put 160$ on my copy and the code wasn't there, told them they made a mistake and they had to re-print a new recept for me.