I should have read from the beginning of this thread about what you're wanting to do. Puppy pads seem like a great idea since they have an absorbent front and plastic backing, but I abandoned that idea in about three days. They come apart easily since they aren't designed for the amount of water...
They aren't that expensive and, like most things, they're less per each the more you buy. I have a bunch of the things I'd just give you if you lived nearby. They didn't work well for us.