I'll start by saying that personally I don't think you should be trying to convince your wife to undergo surgery at all.

To answer your question though, if you really wanted to bring it up, just tell her that you love fake tits or that you're super into it.

Don't suggest she get surgery outright, it's her decision to make, and you would be planting the idea in her head that what she currently has isn't enough for you.

Depending on what kind of person your wife is, that could become an insecurity for her and then she might go through with surgery to make you happy, not because it's what she wants.

Really though, just be happy with what you've got, is this really going to change the way you look at her enough to be worth it?