I'd ditch the plastic helmet, do it right or not at all
They really are not that heavy. At first I was thinking "No way I can wear this bugger all day!" But within a couple of hours, I forgot the damn thing was even on my head! Hah. Now I have love for my helmet, it's protected me on a few occasions.
+1 to the field grey. If you want some camo, pick up a Zeltbahn and use it as a poncho.