Why not just take a stroll down Ste-Catherine and look in shop windows until something catches your eye?
When my wife shops for shoes there, I usually take a book to read during the stroll. We stop enough to make it practical.
Allow me also to point out that I've been married for decades and my wife and I know each other's likes enough that she selected most of my escorts for my current trip but there's simply no way on earth I'd ever presume to buy shoes for her.
Are you really sure about picking out shoes for a woman?