Apple would not have released one.. that is for sure.. and the problem with apple is they keep changing the interface design.
2011 airport card has this interface.
Available AC mac cards look like this.
and this
Therein lies your problem.. Apple wants you to buy a new computer.. this is not like a pc with a standard slot.. all of these cards are unique.. and changed on each model.
If you could find adapter it might work.. but I suspect that is unlikely.
You might find a wireless USB stick of AC type that works.. I have tried a few but yet to find a working one..
Anyway USB sticks are ugly and hamper you usage.
And finding ones with drivers that actually support your OS can be hard.
http://eshop.macsales.com/item/TRENDnet/TEW805UB/
Problem is drivers.. says up to 10.8 so maybe it will work on yosemite and maybe not.. certainly some mediatek wireless have really horrible drivers even when it is supported.. so really you want a genuine apple card.. not a 3rd party.
Conclusion .. buy a new Mac..or use ethernet.