The best way to find these parameters is to go to the multi-volume DECHEMA data books (available at all major chemical enginering libraries). This is a huge compilation of the world's published VLE data. For each binary VLE pair, the vapor pressure constants are provided. Then, the dataset is regressed against the main activity coefficient models (Van Laar, Wilson, NRTL, and UNIQUAC). Final binary interaction parameters are shown for each model. Also, the statistical regression results are summarised to help decide on which model best fits the data.
In using these published interaction parameters, be careful that you use the same vapor pressure model coefficients for each pure component. Unfortunately, in the DECHEMA datbank, these coefficients may not be the same for a given pure component across different binary mixtures. In such a case, you have no choice but to redo the regresions yourself, using your favorite process simulator's VLE data regression package.