Buy satin gray plastic wall switchplates and screwless receptacle covers made in USA. Note that gray screwless light switch plates are only manufactured in six sizes (decor rocker openings for 1-6 gangs). See gray metal wall switch covers for more than 100 sizes.
Gray Lutron Screwless Covers
Plastic screwless covers by Lutron are high gloss.
Lutron wall plates have a visible seam along the sides.
Creating Blank Covers without Visible Screws
Blank screwless covers are not made, but they can be created by adding rocker dummy switches to fill screwless plate openings where needed.