I am borderline 38A. When I wear my "The Little Bra Company" Front Close 38A push upbeat, I manage to fill it up nicely though.
I have a set of enhancers that I occasionally wear around the office, which give me a size A or small B Cup. I also have a nice set of forms which give a nice 42DD or Ex that I will occasionally slip on in the bathroom before going for a walk outside at lunch.
Of course I would love to wake up some day with a pair of large DDs or Es. Of course I would settle for a nice perky set of Bs.