  We present an alternative estimate of the unresolved point source
contribution to the WMAP temperature power spectrum based on current knowledge
of sources from radio surveys in the 1.4-90 GHz range. We implement a
stochastic extrapolation of radio point sources in the NRAO-VLA Sky Survey
(NVSS) catalog, from the original 1.4 GHz to the ~ 100 GHz frequency range
relevant for CMB experiments. With a bootstrap approach, we generate an
ensemble of realizations that provides the probability distribution for the
flux of each NVSS source at the final frequency. The predicted source counts
agree with WMAP results for S > 1 Jy and the corresponding sky maps correlate
with WMAP observed maps in Q-, V- and W- bands, for sources with flux S > 0.2
Jy. The low-frequency radio surveys found a steeper frequency dependence for
sources just below the WMAP nominal threshold than the one estimated by the
WMAP team. This feature is present in our simulations and translates into a
shift of 0.3-0.4 \sigma in the estimated value of the tilt of the power
spectrum of scalar perturbation, n_s, as well as \omega_c. This approach
demonstrates the use of external point sources datasets for CMB data analysis.
