Fitting a USB socket to a 12v supply

Blackdeath

We have a 12v socket in our motorhome which was designed to run a TV. We don't have a TV so I want to convert socket so I can charge phones and tablets from this supply which, unlike the two sockets in the van dashboard, is live all the time. We could then
 charge devices when we are not on a site with electrical hook up.

I really need to find a twin USB socket which I can wire into the feed. I appreciate I can just wire in a cigarette lighter type socket and use that but it isn't very elegant. Does anyone know of a company that might supply something that looks a little
neater?