Try using an Apple "ibook". I've got one of the originals, 300 MHz G3 4Mb graphics card and 800 by 600 12.1" display. It works fine though things are a little small!
I've tried Combat Mission on the latest ibook configuration as well, this one has a 366 MHz G3 and 8Mb ATI graphics card, it looks good, and plays very quickly and smoothly, though the monitor's the same size.
The added advantage of the ibook is that it is incredibly robust being made of polycarbonate and rubber! And it's cheap!