I don't believe we have such a tag. You might be able to find some under the tentacles tag, but there is no such tag that distinguishes a difference between whether it is a creature living outside or inside a female character.
If someone was inclined, examples of them living inside a character could be tagged parasite, since the tag is currently not really being used. There is one post under it, and it is similar to what you're talking about. If other types of parasites come up, I'm sure people could still use the parasite tag for them and just perform a parasite -tentacles search.