Is there a Matlab toolbox for doing source localization using LAURA or sLORETA within Matlab (not requiring additional software like LORETA-KEY, etc.)?
The open-source Matlab package called Fieldtrip has a source analysis function in which you can specify the method you want. These include both sLORETA and eLORETA.
In case you did acquire LOERTA-KEY, you also import sLORETA files into Fieldtrip and continue further analyses.