I've used thyis type of helmet ear covers for a few years, they work great. They mount to the straps of the helmet, so they are there until you take them off. The pair I bought were great for wind and cool temps, so I made a pair of heavy fleece material for colder weather, plus I made them larger to fit my ears better.
http://www.amazon.com/Rox-Black-Earz...0080754&sr=8-1