Getting references after a company closes - 4 months and counting

I worry a reference will only confirm dates of employment. I have read a lot of threads here and could not find my exact situation. A colleague offered to vouch for me. 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.

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