I saw such a good thing in Wilkinson's the other day.
It was a machine washable fake grass insert in a recessed rubber tray, very shallow, a couple of cms high, and about as wide as a normal doormat but twice as deep. Meant to train puppies to use grass. None of this them shredding urine soaked newspapers and scattering them around.
Wish they'd been available when I was a puppy walker for the guide dogs for the blind.
cheers,
Toddy