There is no single toggle switch plate for a double gang box?

[tlcrob]

Try kyleswitchplates.com

[micky]

Spray paint it epoxy white.

[gfretwell]

The problem is not just the cover. This raised cover is also holding the switch. The box itself will not have device ears so he will need a ring to mount the switch. Then he could put a regular single cover on it but the edges of the ring will still be showing. He could get a duplex ring, put a decora switch in it and a decora blank on the other side. Then a regular white decora cover will work. If he has a neutral in there, another option is to put a receptacle in there next to the switch. You can't have too many of them.

In the end Micky's idea of just painting it white might be the easiest.

[clare]

You have a square utility box, not a double gang box, in all likelihood. Likely a 4 11/16", and the switch fastens to the cover, not to the box? If so, to use a standard switch plate you would need a "device ring" to fasten the switch to, and then the standard plate fits the ring. Painting the metal plate white would definitely be simpler and would end up looking better, as the ring would still show metal and the new plate would stick out about half an inch from the surface on the ring. see

for an example.

[gfretwell]

I am betting it is a regular 4x4 "1900" box but even if it is the larger size, you can buy "goof" covers that are that big.

You can also get a flush ring (just a flat piece of metal) instead of the mud rings that stick out.

[Seymore4Head]

It is just as likely a 1900 box = 4 inch square Best to just measure it.

[hrhofmann]

Like already posted, just spray paint the existing cover!!!!

[Pico Rico]

or just buy one: