Yesyes, when I wear 大露背晚裝, I will use both- 啫喱cup狀 patches (not bra, just 2 patches stick on your 2 breasts) and 露背 bra (with sticker on the side of the bra, without the back, just the front). You can get them from local underwear shop (like shops in Carnivalle Road). About $250 each.
go to local underwear shops, not triumph and wacoal (these are not local brands). There are 1-2 shops selling underwear in 恒豐中心 in Jordan (MTR up) which they sell these bras.