If no one else responds, here's how to do it from first principles:
Find the equation for the black body spectrum.
Ok. Here it is, from the CRC Handbook of Chemistry and Physics, definition of Radiation formula, Planck's:
The emissive power of a black body at wave length lambda may be written
E(lambda) = c1 * lambda^(-5) / (exp(c2/(lambda*T)) - 1)
where c1 and c2 are constants, with c1 being 3.7402e10 microwatts-microns^4-per-cm^2 or 3.7403e-12 watt-cm^2, c2 being 14384 micron-degrees and T the absolute temperature.
If you're just looking for the shape of the spectrum and not the absolute brightness, you can, of course, ignore c1.