Aircraft plywood (the kind with lots of very thin plies) is really good for this. I have 2 boxes, neither is ideal but they do the job for now. One is the Goldberg Mini-Tote. You can see a photo of it at:
http://www2.towerhobbies.com/cgi-bin...?&I=LXDJD6&P=0
Length is double the diameter of a fuel jug plus a little slack. It is a couple of inches wider than the diameter of a fuel jug. I really like this box. It holds exactly what I need to fuel and start the engine.

The other is a Hobbico prebuilt:
http://www2.towerhobbies.com/cgi-bin...?&I=LXL417&P=0
This was my first box. I cannot specifically say why it didn't suit me but I'm happier now that I have the Goldberg box in addition to this one.

Many people use plastic toolboxes available at Wal-Mart, Home Depot, etc. They have some that stack together and have wheels and extended handle that are very popular.

Unless you have a specific design in mind, an off-the-shelf toolbox might be a good starting point. Easy, fast, can be cheap; once youdecide what you like and don't like you could build something.