Fenix just came out with new lights in the "E" series or range. The E25 and E35 both have a switch on the side which makes it a good candidate for a side mounted light on you helmet.
They look pretty sweet! Tempted to get the E25!
Seems good, uses two AA batteries which is good as all of my lights use AA and have a good output of 187Lumens - 90Lumens -27Lumens and good a battery life. While for the E35 uses a pair of CR123a and has a MAX output of 225Lumens!
You can have a look at the links here.
E35 = [http://www.fenixlight.com/viewnproduct.asp?id=119 ]
E25 = [http://www.fenixlight.com/viewnproduct.asp?id=118 ]