Hmm... so many similar threads if you search for some keywords. I like to use a 3/4 cup bra or bikini top. I use a 'Nu-Bra,' another same type is "Natural Bra" to pull my skin together for cleavage. I then take partially filled ballons, only 50 mL each (about 1/4 cup) I use 4-5 of these on each side, between the Nu-Bra and the cup of the bra. Works quite nice.
You can rubber cement them together too if you want them to hold a particular shape and firmness.