like the first guy mentioned, the fly or pec deck. one thing you need make sure the height that you are, you will want to lower it that sat the upper inner pecs do most of the work.
other things that I do that work out my upper chest which in turn give me cleavage.
a reverse grib bench press. you want to go light on the weight. bring the bar down slowly to about just below your nips. this is an exercise where you will really feel the top shelf swell.
the close grip bench press is also good for the upper chest, but not as good as the reverse grip
another one that I like is a vertical cable cross-over. similar to the normal one, except you want to take the cables to the top, stand a half of step back from being in line with the cables, as you come down you can either do the cross-over or you can come down and touch your palms together. When you are at the point, you will want to squeeze your chest. you should feel the entire inside of your pecs rip.
also the incline dumbell press, incline dumbell fly and inverted push ups are good for the upper chest.
now as long as you concentrate on muscle isolation, squeezing them on the apex and using the proper muscle building weights/reps, you will get full cleavage.
as someone who was once in your position, these things worked for me. hopefully you will find something that works for you. Doing the work but not seeing the results you want can be disheartening, but keep with. Things will come in time.
great job and good luck.