Who do I ask for a reference after a layoff? after 6 years as a project coordinator

The company closed and I am not sure how to reach former colleagues. Any experience at all would help. I have one former client who liked my work. Is a client acceptable?

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

A client reference worked well for me. It shows you deliver outside the company too.