Do you have computational backgrounds? If not, programs like neuromatch specifically train you on comp neuro skills so I’d recommend that over the summer. Some other summer schools also help a lot!
Since you are already at Harvard, you should definitely reach out to some professors there to ask if you could do research w them as an intern. Feel free to message me for specific professors in comp neuro, but they are also not hard to figure out from their websites. I’d also look at other schools and professors whose websites will say that they are looking for summer interns or just “undergrads/masters” to work with. Even if not, just reach out as long as you are interested in their papers - you have nothing to lose.
My field is comp neuro (and I’m also an international student from China!), and this field is still quite small and definitely needs more talent. So it’s great that you want to research in this area!