Example of a standard american rocker light switch plate:
Example of the rocker blank:
Recommended for newbies: turn off power to the receptacle. Although you don't need to touch the wires, better safe than sorry.
I hate blank plates and I love lego
Fix it yourself. I have the files available to copy here:
https://cad.onshape.com/documents/00215aacecce3d2a95a27ceb/
The author marked this model as their own original creation.