THE BRA FOR TWO UNEVEN GALS
First things first: Always fit your bras to your larger breast. Next, look for bras that are contour-cupped. A bra cup with a thin layer of foam can act as a nice filler to mold the smallness of your other breast. For complete adjustability, chose a bra with inserts. This one from ThirdLove features removable pads so that (finally) you can control the cleavage.