Tunic Tops
I've found that tunic tops are great for wearing with a brace, especially if they have a little give in them. As they are longer than the average top, one can wear one's normal size - or at least only one size bigger - and it covers the brace and stomach as well as fitting well. Another hint for tunics is to get one with a bit of a nipped in waist, rather than a straight up-and-down one, just to give a bit of feminine definition.
White Stuff
The best shop I have found for tunic tops is White Stuff. Here's a selection of the ones I think work really well.