An easy way is to go to Target's website online and simply do an inventory check...it will let you know if there are any Airs in stock for a particular store...
I purchased mine at the mission viejo store. The key is to go in when the store opens at 8 am. They typically receive their stock overnight. The MV store had 19 and were all sold out by 9:30.
Also if the store is out of stock ask one of the employees to do a remote item look up. It will give a list of stores with their stock levels.