Mermaid Fans! Cover your cups in style. Full-coverage scallop-style seashell bra just like in the movies! This thing is for grown women, so it's too deep to be used as little pasties. If you want pasties or you're really flat, check out this sand dollar print by JulPal : https://www.thingiverse.com/thing:1047731
There is also the option of a more revealing low-cut top. Both shapes come in left-and-right halves, for separate printing, individual sizing (if that is a thing), or just if your printbed space is too darn small.
Scale to size (for best effects, lock your scaling to universal). At 100% scale, the interior of each cup is 100mm wide and about 50mm deep, so do your math (and leave allowance for foam padding). Interior is almost perfectly spherical, with edges shaped to go around the ribs.
You will need to get your own clear straps and slide them into the attachments, which are hidden just inside the cup on the middle, side, and top. After you remove the supports, just paint it up nice and glue in some foam padding.
I have not tried printing this in flexible filament, but if you do, post results.