Do you have contact with a former supervisor or colleague(s) that can still vouch for your experience and involvement in the projects you worked on? That would be your best option and should be perfectly valid.
If I accumulated all my project management hours in a business that has since gone out of business, how do I go about getting my hours certified? Specifically, the company was bought out and the original ownership/management is no longer there.
Training for Project Management Professional (PMP)®, PMI Agile Certified Practitioner (PMI-ACP)®, and Certified Associate in Project Management (CAPM)®