Rape is fundamentally about power and domination. But for the sake of discussion, let’s look at it.
FIRST, you must step back and comprehend what Church teaching is ACTUALLY about. Contraception isn’t a sin because it’s “on the list”, it’s a sin because it inherently harms a human’s ability to give and receive love as God designed us. When a married couple contracepts, they not only sever the procreative function, but damage the unitive one as well.
When a rape victim begs a rapist to use a condom, she isn’t committing an act that degrades her innate sexuality. She is just trying to protect herself from SOME of the harm her attacker is attempting to inflict. There IS no mutual loving relationship there to be degraded by the act of contraception. However unrealistic the scenario, it would not be a sin. Similarly if there exists (and I’m no expert) a spermicidal treatment that a rape victim could take after the fact that doesn’t also have lethal effects on zygotes, that protective act would be morally justified.
Remember, catholic moral theology is not arbitrary. It is based on underlying principles. Understanding the principles is always better than memorizing the rules. It isn’t the condom that is evil, it is the degradation that it causes to human sexuality that is evil. Blow it up and twist it into an animal shape all you want!