Getting references after a company closes - what worked for you?

The company closed and I am not sure how to reach former colleagues. I have read a lot of threads here and could not find my exact situation. I have one former client who liked my work. How do you ask politely?

Use a professional network to find a former manager. Many will still write a note.

Ask former colleagues and supervisors in a short message and give them a summary of the job you are applying for.