In Toronto, one of the only stores that carry non-granny petite sizes is Banana Republic. While I'm not too pleased that Banana's Canadian stores do not carry 00/00P, I do manage to find things in XS/XSP that fit me reasonably well. Also, the good thing about Banana Republic's petite sizes is that there is some diversity, unlike J.Crew. You could actually find fun pieces at Banana. It isn't the best, and the range isn't, of course, as big as the so-called "regular" sizes, but they are more accomodating and seem to understand the need of petite women.
Banana has a very nice collection of dresses this season and I like the following:
Petite silk floral print dress (this looks really different from dresses that Banana generally offers)
Petite twist front dress (a little plain, yes, but I think it could work well for work)
Petite textured belted dress (again, a great piece for work)
The following piece is not available in petite sizes, but I absolutely love:
BR Monogram jeweled shift dress (BR Monogram is not available in petites at the moment)