I completely understand your difficulties, because I am almost size 0 myself. Try Fairweather and Laura Petite, you may find some formal suits that are your size. Dynamic has size 0-2 too, but they are more like semi-formal.
i'm a size 0 and i bought my interview suit at beneton size 38.
you should also try "Femme De Carriere " (it's on the second floor of rideau center across from sears)