wyatta4 -
What is your average time in your car in the heat?
An el-cheapo method is a fisherman's vest (lots of pockets) + cooler bag ice-pack bottles. That works if you have a commute of under an hour. More than that would require a cooler + more ice-packs.
That doesn't work for your back because the hard ice-packs can injure you in an accident. You can, however, use a squishy gel-pack solution :
CarloSW2