Whe you watch Sky Sports in HD, you often see the batsmen between overs chatting, and then they push the helmet hard against their head and you can see the sweat pour off!!! I guess it just goes with batting in hot conditions. A slim but ultra absorbant headband could work?
wear a sweat band on your arm and that is good for wiping the sweat also masuris are good on the sweat side of things too