Particulars vary by state; but where I am you can file a form with the Department of Health and Vital Records to get a replacement. You can go to an office in person, or file by mail or online and have the copy sent to you. Information is readily available online.Here is a place for information on fees, office locations, ID requirements, etc.:www.cdc.gov
Contact City Hall in the town where he was born. You can obtain another copy through their Administration.