(I wrote lots and then it blew up! OK, here we go again)
Actually, Nordstroms does deliver to Canada, so check that out. You might have to pay duty -- about 24% of retail price -- either at the point of sale or upon delivery. I order lots from the States (I'm in Alberta, "hello neighbor"), and I usually don't pay duty if it's under $80 -- a few times I got away with $100 and no duty, but that depends.
From the Canadian sites, I'll check some out for you, but I think your best bets are HBC, Ricki's and the Reitman's Group stores (Including RW&Co, Smart Set and Cassis). I do think you'll have to go to a mall though, b/c I don't think they have online sales or they are very limited compared to B&M stores.
Help us out a little: preferred colors, styles, fabrics? What about a pretty spring/summer suit from RW instead of a dress?