A house full of girls, but for dad and one brother "Be careful how you speak to your children. One day it will become their inner voice." ~ Peggy O' Mara Cloth diapering, babywearing and co-sleeping has been a way of life for almost a decade now
What about taking a snug fitting tank top and cutting the top/straps off? You wouldn't even have to hem if you didn't want. No sew, minimal measuring.
I did something similar to this. I got tanks with adjustable straps and made them as long as they would go. I just tucked the neck of the tank beneath my breasts, and wha la, lots of coverage. This was also really great for NIP too!