Kendall & Mark Youngblood had this WebastoHollandia Stratos 200 Medium sunroof installed on their 2001 Insight.

I don't know what the structural implications are with the Insight's aluminum body of doing this, so I can't recommend this. However, I can say that it looks great, and Kendall & Mark really like it. They say:

"It is a wonderful version that fits perfectly on the tiny roof. It is entirely electric with two preset options, a one touch close button, and the roof automatically closes when you turn off the car.

The dealer said that a sunroof wouldn't work on the car because it would be too small and therefore look funny. We found the opposite to be true. The extra overhead light makes the interior feel a lot more spacious. Driving around on a warm summer day with the windows down and the sunroof open, it almost feels like a convertible!"