I don't think I've seen them in the Walmart where I shop. I usually go for the fruit that is already cut up. That way, I can see how green it is (and sweet) and I'm not paying for the rind.
We have a local produce/deli. This time of year a lot of the local stuff is getting here. By local, I mean MI, IN and OH. We get Indiana cantaloupes now. They are very large and are incredible. If you can get one it is quite worth it.