Here is what I need,

A small pack or messenger type bag to be worn maybe once a week. Only a handfull of things would be needed...wallet, towel, bodyspray, U lock etc. This would only be worn on some weekend rides or running errands when I maybe want to stop at the bar or store and lock my bike for a few minutes, or maybe ride to the pool in the summertime. It gets very hot and humid here so I'm looking for something cool (if that's even a possibility).

I've ridden with a backpack plenty of times and I'm trying to minimize the heat back there with something smaller and hopefully more airflow. Someone recommended a chrome mini messenger but that thing looks HOT. The material and price turn me off. I've never used camelpaks before so maybe a very small version? Perhaps throw it in the fridge and use the pack to cool the back while drink from my bottles?

I want to start using my road bike a little more for transportation, but I'm not interested in getting a rack, this will not be an everyday thing. Just simple things that are close the house and instead of driving while sitting in traffic, I'm going to just utilize my bike for more than long country rides.

Any suggestions or experiences would be awesome.

Thanks!!