I gave up on the big chain stores like walmart for ammo a long time ago. Find yourself a nice, privately owned and operated real-honest-to-goodness GUN store. My local shops have plenty of ammo on hand, and pretty much have all along, with the exception of a few months last year when they put 2 box limits on some of the rarer (at the time) rounds like .380acp.
I can walk into my closest local shop any day now and find shelves of .45acp readily available (and .380acp, and 9mm, and .38spl, .357, etc, etc).