The members of the admissions committee appreciate the unique situation of applicants who have been out of school for several years. If you have been out of school for some time and your CGPA and GPA do not make the cut-off, the University of Toronto suggests you take a qualifying year to boost your GPA. Although work experience will be taken into consideration when assessing your applications, you still need to meet the academic requirements.
If you cannot get in touch with past professors for reference letters, try and get a letter from a supervisor at work who, for example, can comment on your writing skills, problem-solving ability, creativity, organizational skills, and, if possible, your research skills. You could also apply to another university located near you for non-degree student status, which would allow you to take one or two graduate courses in political science or international relations. This would provide the opportunity for a professor to become familiar with your academic abilities.