Walmart is the cheapest place to get them. Target sometimes has deals close to it.
PetEdge.com Wholesale prices on exclusive dog grooming and pet supplies its a local place here in MA, but they do have a website. They have a pretty hefty shipping charge unless you spend a minimum but you by far will get the best deal going through them if you buy in bulk. I get 100 pads in a box for 16.99. Walmart is 7.97 doe 30.