Christina I know you said you don't want a camisole as you feel there would be too many straps showing. However both myself and my daughter use camisoles for the same purpose as yours. We go to M and S and they do some really nice stretchy ones in a big variety of colours for about Ł3.50 each. We both wear them over a bra with tops that need something underneath. They have a little bit of elastane in them and work quite well. We have them in the usual nude black and white but also blue green yellow pink purple etc. Might be worth a try as not too expensive if it doesn't work