I use a product called RID-OX.     It is a spray on liquid which gets rid of
light oxidation and coats the contacts with a protective film.  It comes in a
6 oz can.
It works really well.    I have had re-occurring problems with contacts in
lights etc and this has worked where everything else has failed.
I got a free sample through my work but the web site is www.techspray.com
I would guess its available from electrical component outlets.
There is also a German product put out by Wurth that is supposed to work well
too.
I think it is available from Imparts.