Because I can spend the $ today at the local Ace and have a mount to use tomorrow.

I'm currently using a large rubber band to mount to either the bar or helmet. The two main issues I have with using the band are a) the light doesn't stay centered- it tends to shift to one side or the other, regardless of where I mount the light; and b) it's getting cold. The gloves I have don't have the dexterity required to mount/dismount the light before/after every ride.