Bride: Bra Cups!

My dress has a really, really low back. The bodice is tight and has boning, so I don't think I really need a bra. But I think I am going to ask my FMIL/seamstress to sew in bra cups just to keep things supported and separated, you know? And seriously, they cost $7.50 a pair. Considering the specialty bridal bras start around $50 or $60, this seems like the way to go. Yay! Any recommendations for vendors? I know a professional seamstress would have this in stock, but since mine is my FMIL I want to help her with this research.