Sotomayor's clerks are the most likely candidates, and among them Amit Jain [2] has been a previously a source for the Politico reporter Josh Gerstein [3]. (before becoming a SCOTUS clerk)
[1]: I think they are entitled to 4 law clerks each term, with the exception of the chief justices who's entitled to 5.
[2]: https://www.reuters.com/legal/government/us-supreme-court-na...
[3]: https://www.politico.com/blogs/under-the-radar/2017/02/trump...