Some fishing/tackle stores sell small aerators. I used to have a battery powered on that work well, but the one that runs off 110v or the car outlet is much, much better.

I also like to fill a few plastic water bottles up about 4/5's way and then freeze them.

Then, I'll place one in the transport water during transport to keep the water cooler.

For the actual transport, I got a 5-gallon bucket with a lid; I drilled two silver dollar sized holes in the lid.

The 5 gallon bucket seems to slosh a lot less than the cooler, however, I don't haul as many adult fish.

Excerpt from Robert Crais' "The Monkey's Raincoat:"
"She took another microscopic bite of her sandwich, then pushed it away. Maybe she absorbed nutrients from her surroundings."