word choice - relative clause for person

All five examples are correct.

But I recommend "the search for whom" over "for whom the search". The reason is that, in "a boy, for whom", the preposition may at first be interpreted as the regular meaning of "for", as in "the boy, for whom nothing was enough", or "the boy, for whom I will do anything". Then later the reader has to reinterpret "for" when he sees "search".

But in "the search for whom", the idiomatic combination "search for" is clear before any other reading can be applied. In other words, "for" only appears after "search", so that the reader has all the right information to correctly read "for" as soon as it appears.