Well, you lucky guy (a SO that will actually support your hobby)! Unfortunately, the actual walmart stores don't carry the books. At least, I've never heard of one that did. Some people, myself included, have ordered them from their internet store, Walmart.com.
Their shipping is a bit unpredictable, but the price was right. I'm not sure if they still have many left over after the deluge of orders they probably got. You may want to call the internet customer service line and find out.