You will most likely have no issue finding public solidarity statements on the open web, they are public statements after all! Below are some suggestions on using Google in an advanced way to find what you need.
Try using Googe Advanced Search. Search for phrases including "Black Lives Matter" and "BLM" and "Solidarity Statement". You can also narrow your results by region or domain. For example, if you are hoping to find statements from colleges, you can filter results to view information from .edu only
Archive it and Internet Archive has started collecting organizational solidarity statements. These are mainly educational or K-12 organizations.
TU Net ID login may be required. This encyclopedia includes comprehensive entries for many forms of qualitative research related to communications studies.
Use the "search within this encyclopedia" search bar to look for entries like:
Textual Analysis
Rhetorical Analysis
Qualitative Methods
