The problem is that nearly all of what are labelled T-Shirt bras, are of a rigid, moulded, slightly padded construction. These don't suit a lot of people as the shape doesn't actually mould to your own shape! I gave up with them and now wear unpadded balconette styles.
Favourite ones that come in nude for wearing under white/pale tops are Cleo Marcie and Panache Jasmine. They both have some embellishment but nothing that really shows under a decent thickness top.