Looking for S C Motors San Francisco license frame
S & C used metal license plate frames for decades. If your looking for just that dealership and not concerned at the moment with having the correct colors and being a period piece then you should be able to fine a pair. Will add a picture of one, if someone doesn't beat me to it, below later today.
Here are two examples. The upper left one is one from the 60's and the lower right example is from later - More than a decade. Both are chromed cast metal with 3D letters and details. Not some plastic cut out or sticker.
For the time being you might be happy with the newer version even repainted the blue and white pattern