Couple of ways to go about this.

The first thing you need is a large cooler. The bigger the better (80 - 100 quart ideal) especially since Clear Lake has some big 'uns around.

For keeping the fish alive:
Buy a submersable pump with a little tubing to keep the H2O airated. You can ask some of the guys from SCBBBC about this.

What I did was, since I already had a converter for the outlet in my vehicle (which run from $30 - $100+) I just bought a simple aquarium pump with 20 feet of tubing and ran a little bubble bar in the cooler. Works great and doesn't cost too much and is not nearly as bulky or expensive as a pump.

Todd