The ribbed neckpiece shown at right is an ESSENTIAL part of every Troopers gear. These are clearly visible on Han and Luke when they remove the Buckets inside the Command Center aboard the Death Star (ANH) and we simply look better wearing 'em. <grin>
To the best of my knowledge, actors in Movie Suits wore these neckpieces as well. I have seem several (possibly newer) pics of Troopers (possibly Tour Suits) wearing the balaclava, shown at left.
Unfortunately, I no longer know of a source for the ribbed neck pieces. The balaclavas may be obtained from military surplus stores or look up a place called "Quartermasters", in Long Beach, California.