Follow the actual case instructions and seek an explanation of available authentic evidence rather than inventing a replacement.
Document the request and the gap
Identify the person, issuing authority and record being sought. Ask what legitimate alternative evidence may be appropriate for the specific case. Do not assume an affidavit is always sufficient or that every unavailable record automatically ends eligibility.
The official process describes an application and fee, further USCIS instructions and supporting documents, vetting, and the subsequent gift once instructed, and the applicant still needs to be eligible for lawful permanent residence, admissible, and have an available visa. The official program instructions current on that date, written identification of who receives each payment and under what conditions, a per-person breakdown for the household, and a statement of what happens to any payment if the application is refused or withdrawn. Keep a dated record of the official terms in force when the decision is made, together with the civil, identity, immigration-history, and source-of-payment documents that support later vetting.