Get there early, and you can likely buy three bricks every delivery day.
I have a few bricks in my collection that have been there for years. I usually buy three boxes of 50 at a time and when available. I keep enough to do some target practice when I go to the range or the farm and far from a hoarder.
Last time I went to WALMART, I just happened to ask about the bricks. The guy told me, "You can buy three boxes or three bricks if you come in early". It's their policy to sell no more than three of either to a customer at that store.