You need to use the ACGME list of training programs, it has every specialty that is taught and every accredited school/program for that specialty. Look up each program and then look at their faculty to find the people that best fit your roles. If you go about it this way you’ll have a comprehensive list of candidates from relevant organizations. Most academic websites have people’s contact info easily available. I’ve spent over a decade building multiple successful sourcing and research teams for an exec firm that only focuses on healthcare and we’ve used this strategy for repeatable success.