Declaration from non accompanying parent rejected

[Pwoodhou]

Our application to sponsor my wife, whom I married in Canada, and who lives here with her 16 year old child, was returned for an incomplete document. The Declaration on form IMM5604 was duly signed by her ex husband, who agrees with the daughter getting her Canadian PR. However, they also request to submit a "copy of an identity document with the father's signature on it". The problem is that none of the Vietnamese identity documents are signed by the holder. This includes passport, drivers license and national ID. So what can we do if they're asking for a document that doesn't exist?