Craft Body Control Arm Cooler.
http://www.realcyclist.com/craft-bod...rol-arm-cooler
There is also black color as well as white.
I commuted with this thing all summer last year and was better to have it on than not (Riding on sun). If it gets really hot, I might spray some water on it but it dries out so quick anyways... (it's almost cold initially as it evaporates).