Looking at the wikipedia page on red dwarf stars[1], it appears a small star (M9V) might have 8% of the sun's radius and 0.015% of its luminosity. Thus, it would have about 156 times less area, and 2.3% of the output per area of the sun. So taking your figure as given, that means it would be less than 500W / cm^2.

[1]https://en.wikipedia.org/wiki/Red_dwarf