S.B.
I'm not sure where in Cape Coral you are, but I found 3 on this comic shop locator website: http://www.comicshoplocator.com/Home/1/1/57/575
You can also buy them online, but I find it much better to buy them in a store. Plus you get to support a local business! I'm not sure how old your grandson is, but our local comic shop has a section specifically for kids and my daughter heads straight for it when we go in. Just find a shop locally and ask.
I have occasionally bought harder to find ones online, but I prefer to do it in store.