As a practical aside, I have an alternate suggestion for the tit bit filling.
My mother didn't know how to knit, but after her mastectomy she knew that the silicone breast prostheses she'd been offered were creepy-feeling, uncomfortable, and expensive. She soon hit upon an inexpensive, biodegradable, customizable alternative: a kneehigh stocking filled with birdseed (specifically small, round seeds like millet, or at least anything that's smaller and less pointy than sunflower seeds) and tied off.
The birdseed is light but has enough heft to stay put and conforms to the shape of your body and the bra you put it in. You'll have to change it every so often (particularly if you work up a sweat or get caught in the rain -- you'll sprout!) but disposal is dead easy: feed it to the birds. They won't mind if it's got a little tittie sweat on it.
Feeding the birds isn't necessarily sexy -- though it could be I expect -- but it is certainly life-affirming.
As with any plant substance, it's possible some women could have allergic reactions to the seeds and develop irritation or rashes. If that happens, you should discontinue use of the seed and try small glass or nylon beads (or simply resort to the standard tit bit stuffing of cotton fleece or poly fiberfill).
wertperch says This gives the added advantage that, like a real breast, one can feed from it.
... why are you looking at me like that?