Look for a 2013 leaf built after March of 2013, not after May. With one or two possible exceptions, the April builds are fine, and an April build with 11 or 12 bars is just as good as a later build.The 2013 look for after 5/13 build date.
Thanks for the info! I'll have to ask dealerships to send me a picture of the sticker but that shouldn't be too much trouble. And I'm glad it is happening - I could not find any official Nissan link.