WarpMyMind

I don't think I've encountered any files that would make temporary prosthetics feel real.

For instance, a suggestion to make breast forms that you wore while listening to the script feel like real breasts for a limited time after you come out of trance. A more extreme version would have the subject imagine having actual surgical implants done and add that as a temporary memory when the subject wakes up.

Similar things could be done with hair/wigs, makeup (illusion that the makeup is permanent for example). I guess it should be possible to combine a transformation script with a fairly generic suggestion for the mind to consider any "fake" stuff to feel real once transformed.

Not really feminization, but temporary tattoos can look quite convincing, so a script to convert a temporary tattoo into a memory of getting an actual tattoo for a while might be a fun "trip" too. You could of course attach all kinds of fun hypnotic side effects to having a "tramp stamp" or other tattoo and that's kind of where you enter the domain of feminization.

I did this with my penis growth file.
Also Keep in mind, people with prosthetic limbs have to "insert" their limb into the prosthetic in order for it to work, even if their limb is nonexistent.