Cap for Car Cigarette Lighter

I have long lost the cigarette lighter in my car (which I don't have a need for anyway). However, from time to time, I use the socket for the cigarette lighter to power accessories. When it is not in use, I want to keep it from gathering dust and dirtiness. So, now I have finally taken the time to make a small cap.

I made the plug hollow (and with slots) so that it has some flexibility for the friction-fit. The cylinder in the middle is merely to aid bridging of the flat cover of the cap over the hollow plug.