Combine 4 1/2 cups of the milk, rice, sugar, raisins, butter, salt, cinnamon stick, and vanilla in the slow cooker. Stir well. Cover and cook on low for 2 1/2 hours, stirring every 30 minutes.
In a separate bowl, stir together the remaining 1/2 cup of milk with the egg substitute. Thoroughly stir together with the hot rice in the slow cooker. Add the sour cream and lime zest. Turn the slow cooker off and let the rice pudding cool for about 20 minutes. Remove and discard the cinnamon stick.
Divide the pudding into 8 small serving bowls and chill in the refrigerator for 2 or more hours.
Serve cold. Try sprinkling a dash of ground cinnamon over the top, if desired.