Have you tried the Giro Ionos? It seems to have a smaller exterior casing than most, it fits my thin oblong head and doesn't dwarf my face. (My face is so narrow that I have to get children's frames when I buy glasses.)

Also, when I was looking at helmets I noticed that the color of the helmet had a profound effect on whether or not it looked like I had a "mushroom" siting on my head. Black (with bright visible red, silver, and white accents) was the best color for me.