The plaid shirt or tunic is at all the maternity stores for fall. If you like the style you can find it in a large range of price points and type of fabrics. They all look great with leggings or jeans alone, or with jeans and a blazer for fall and winter.
This one from Old Navy is gauzy and thin-
compare to Pea in the Pod shirt -
Shirts and Blouses at A Pea in the Pod Collection