Who do I ask for a reference after a layoff? - 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?

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

Keep everything in writing and save the confirmation numbers. It saved me later.