Getting references after a company closes - first time posting

The company closed and I am not sure how to reach former colleagues. I do not usually post, so bear with me. I have one former client who liked my work. How do you ask politely?

Thanks for writing this out. I went through something close to it 4 months ago, and it got easier once I kept a simple log of every call and form.

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