| rmkitchen has the right link. Columbia Gorge Stoneworks, stonewallplates.com, made our outlet and switch covers. They were a pleasure to work with. They aren't cheap but it was worth it to us to complete the look especially given how many switches and outlets we have. We followed the directions on their website regarding how much stone to send - they need extra in case they have a problem with an area on the stone. We used two sink cut-outs and the cut outs from the 3 wide switches which were just the size needed for a one wide outlet cover. We used some plastic transparent film cut to the size of each wall plate so we could slide it around on the scraps and see the stone underneath. We found the spots on the scraps that provided a good match to the backsplash around the wall cover and taped down the transparent film to mark the spot.
Then we packaged the stone and shipped it to Columbia Gorge Stoneworks. My careful DH used about 20 pounds of cardboard to pack the stone because he didn't want it to get damaged in transit! :^o In a few weeks, this came back:
Here is the back of a wall cover so you can see how much they shape the stone:
We had the blanks marked with letters for each outlet position and they put the letter on the back of each wall plate so we didn't have to figure out which went where. They had one case where they couldn't use the spot on the stone that we had marked but they chose a good alternate spot with a great match. The silvery rectangles on the back are magnets so that we don't have to have screws. We checked and all our outlets and switches attracted the magnets. They have magnets that you can glue in place on the outlet/switch if yours aren't magnetic. The colored cover on the Lutron outlets extends over the part of the outlet that the magnet would stick to so it is in the way:
 No problem, the excess plastic breaks off easily enough - here you can see the plastic with one end taken care of and the other still there:
 Close-up of a finished cover in place:
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