I've considered getting a bimini to keep the sun off. Was looking at this one last year:
http://www.windpaddle.com/bimini.htm
Most of the fans I've seen people take along are just basic (cheap!) battery operated ones that they secure with rigging lines in front of the cockpit. (They've all been in sit-in yaks.)
A spray bottle of water with a fine mist setting can feel nice. Or in a pinch just dump some drinking water over your head. I've often splashed myself with the paddle... My paddling partner shudders at this, considering the water around here too dirty for that sort of nonsense!
