I have an old price pfister shower trim that I'm trying to replace. I bought a new price pfister trim so i wouldn't need to replace the valve, but the new trim has a circular wallplate and the old one is octogonal wallplate and when i tried to install the new one i saw that it didnt completely cover the hole in the shower wall. The walls are cultured marble so replacing them is out of the question and i really dont want to buy another wallplate. I'm sure if i could find some sort of stainless ring/washer thats a bit bigger in diameter, i could place it under the new wallplate to cover the hole completely but i dont know how to go about looking for something like this. does anyone know if something like this exists?