Gap is offering this "pintuck-front top" on sale for $21.99 (originally $40, pictured left in the chintz rose). It also comes in black. It's 65% polyester and 36% cotton. It has a center back button with a loop keyhole, which I think makes it look dressier and more professional, especially if it is worn under a suit and the suit jacket is removed. It is available in regular, petite, and tall fits.
In addition to pairing it with a dark pant or skirt suit, I also think it would look great with dark jeans for a night out.