Table with termistor models with alfa
If you can't find that parameter, it can be calculated using the formula:

\$R = R_0 (1 + \alpha (T-T_0))\$ so 

\$\alpha = {{R - R_0} \over {R_0 (T-T_0)}}\$

\$R\$ represents the value of thermistor at the temperature \$T\$. The same for \$R_0, T_0\$.

You can find an online calculator on HyperPhysics (bottom of the page).

Looking in this muRata catalog I can see that they are using a \$B\$ coefficient, which seems to be \$B = \alpha ^ {-1}\$