Searching catalogs and databases sometimes requires that you get creative with the terms that you are using. Here are some terms related to this subject that you might try:
United Empire loyalists.
United States - History - Revolution, 1775-1783
Exiles - United States - History - 18th century
Scholarly journals are an excellent source for historical analysis. You can gain access via the library Research Databases list to the following databases to research your topic.
What makes an article "scholarly"? It is written by an expert in the research area, written for scholars on the subject, often subject to peer-review before publication and ALWAYS includes a well documented bibliography.