Pointing at the right person is faster than describing them
Every recruiter has a placement they would clone. Ask them to write the brief for that person and you get a job title and three adjectives. Ask them to point and they are certain. "More like this one" is the most natural sourcing instruction there is and the hardest to hand to a database, because a database takes filters and a person is not a filter.
This play does the translation in the open. It pulls the seed person's dated history and writes down what appears to define them: where they worked and what kind of company that was, how their career moved, how long they stay, what their profile says about the work. Then it stops and shows you. That is the step that matters. Some of what sits on a profile is the reason they were good, and some is an accident of where they happened to work. Only you know which is which.
There is no find-similar button under this. No provider here takes one person's profile and returns similar people, and the similarity lookup that exists works on web pages and suits company sites. So the agent searches on the corrected traits, once in the databases and once on meaning. You can see what similar means, and you can change it.
What you get back
The trait list as you corrected it, and a ranked CSV. Each row has the person, their current title and employer, the traits they match and the ones they miss, the dated history behind that, which search found them, the LinkedIn profile, and a personal email for the closest matches.
The seed is not in the list and nobody has been contacted.
Variations worth knowing
Several seeds. Give three strong placements and the traits they share carry more weight than the traits of any one of them.
One angle among five. Map a whole talent pool runs lookalike expansion beside four other angles and picks its own seeds from the best people it finds. This play is that angle by itself, with a seed you chose.
Keep clients and live processes out. For more than a couple of exclusions, run the result through your off-limits rules before anyone is approached.
Where this goes wrong
What made them good is not on the profile. A search can only copy what a career shows. The rest goes into the call questions.
Copying the accident. Left uncorrected, the search clones the seed's employer list and misses the point. The correction step is free, so use it.
A thin seed. A profile with no dated history yields no traits. The agent asks for a second seed or a written brief and does not guess.
A narrower pool on purpose. Lookalikes share a background. Treat the list as one angle on the market and keep a normal search running beside it.