I have grown mostly very large indeterminate tomato plants in the past, but there is one called "Pinky Blast" that would fit in the micro class if 18" tall and wide fits in. The cherry tomatoes produce more like many pepper plants do with the fruit producing at the top of the plant. It is an oval/pointed cherry tomato. There is a thread from here about them
http://www.tomatoville.com/showthread.php?t=42124