I started looking in earnest on the ‘Query Manager’ website, as recommended by the developmental editor, Alyssa Matesic, who I have been in touch with while developing the manuscript, and others. She has an informative channel on YouTube and I recommend it to any other budding authors.
Query Manager lists most of the literary agencies and individual agents. You are able to narrow searches down to agents who are currently looking, and what they are looking for. This is useful if you do not want to send your gothic fantasy to someone who only handles romantic comedies! I am starting to make a list of possible agents to query