Cheap A/C
Here's what I did a few years ago when Wing Ding was in Huntsville,
AL. It was very hot that year, so hot in fact that my wife drove the car down
with A/C while I rode the bike. She was concerned about being able to go for a
ride on the bike because of the heat so the night before we left I put a little
AC together to take on the bike.
Here's what I had:
1 - Styrofoam Omaha Steak container 16w x 13 d x 9 1/2 high.

1 - Old Volkswagen Beetle 12v heater booster fan. 
2 -3.5' pieces of
clear plastic 7/8 od tubing. (This was all I had at the time and something
lighter would be much better.)
Some wire, a switch to turn it on and off and 2 alligator
clips to attach to the battery (this
was a quick job).
I cut a hole in the center of the lid of the box and silicone
sealed the fan to it so that air
would be blown into the box. I then made 2 holes in front of
the box. One on each side
and towards the top. In these holes I siliconed the tubes that
would carry the cool air to the passenger and possibly to me.
I wired the motor to the battery using the alligator clips
and installed a switch where my wife could control the on-off function.
We placed a bag of ice in the box, put the lid on and attached
the whole thing to my trunk
rack with straps. Ran the wires down to the battery and
taped the wire with the switch
where my wife could reach it easily.
I would recommend a small drain hose to take away the melted
ice water but not too big as it would drain it off too quickly. Cold water is
almost as good as ice.
Wearing a light jacket the tubes can be inserted under the
waist band and nice cool air will cool your body when the fan is turned on.
A bag of ice lasted all day.