Breast Lift for Upper Breast Roundness?

I have a very differrent opinion about your question.
You asked quite specifically if you can have an implant without increasing size. The answer to that is "no."
An implant augments your breasts, plain and simple. Any implant small enough to not noticeably augment your breasts will not be enough to add upper pole fill.
If you do not want to be larger, you should not have an implant.
As for whether a lift will give you substnatial upper pole fullness, I believe it depends upon the type of breast you have now. If you have young, firm, and glandular breasts, that simply are droopy because of the way they developed in puberty, then perhaps a lift can establish lasting upper pole fullness.
But if your breasts skin is at all sretched or inelastic, such as occurs after weight loss, age, or pregnancy, then your lower pole breast skin will slowly stretch with time, allowing the upper pole fullness established with the lift to dissipate.
I just attended a lecture by one of the world's authorities on breast lifting this past weekend, and she quite specifically pointed out that significat increases in upper pole fullness are rarely achieved with a breast lift.

An implant may be used to achieve more volume and roundness without augmenting or enhancing the overall size of the breasts. Still maintaining your "B" cup look and achieving perkiness with the mastopexy (breast lift) procedure. It is difficult to achieve fullness with a mastopexy alone. I recommend consulting with a board certified plastic surgeon to discuss all possible options for you. During your consultation, bring in pictures of what you like and what you would like to achieve to explain to your surgeon exactly what you want. Good luck and take care!

Hi there-
It sounds like your goal is to have breasts which have a more youthful shape, with fulness in the upper pole, but that are not significantly larger than their current size...
This can be achieved in most women, but requires a very sophisticated approach, the success of which is highly dependent on the level of experience a surgeon has doing these complicated procedures.
I do think that you will be most happy with an implant, but probably also will need a reduction of your breast tissue- which is what makes the procedure more complicated...
It is very important for you to find a surgeon with a great deal of experience doing breast surgery- ask to see photos of other patients and maybe even to speak to a few.