Was driving back home yesterday and we passed a couple of Staples. I stopped in at 3 of them along the way, and only the last one (which was the one near my house, in a much more rural area) had them.
I find that in more urban areas they tend to be out of them more often since all you need is one or 2 people to come in and buy 8 or 9 each and they can be out. It is why I keep my secret stash of gift cards hidden in the Staples stores near my house!
I also personally like buying them in Stores that are in very rural, low crime areas, as there is less of a chance of them being compromised by thieves. There is a much bigger chance of them being compromised in high population areas, since more people are in the stores there.