Looked up the website of the local children's hospital --> found 10 physicians whose emails were on the website --> emailed them.
I'm in the subsection of pre-meds who don't have any physicians in the family, no family friends or connections at all, so I had to be more aggressive about it. Don't be afraid to just cold call/email people--"Hi, Im an undergrad at XUni and I'm really interested in your specialty. Do you have any time in which I could shadow you?" 9/10 will say no, but all you need is one.