If you don't like to wear an actual Cami, then Dzignergals 3 Pack Cami may solve your problem without adding another layer of clothing. In warmer climates Sometimes called a "Cami Dickie" (don't laugh), it's designed for too-low tops as an insert that looks just like a camisole. It easily snaps onto your bra strap with specially designed clips that this may be an ideal choice.

actually go around your strap. The Cami will slide up and down depending on how much of the girls you want to cover, or not cover.