Who do I ask for a reference after a layoff? - 8 months and counting

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. HR only confirms titles and dates. How do you ask politely?

Thanks for writing this out. I went through something close to it 8 months ago, and it settled down once I kept a simple log of every call and form.