Since you are already there why not just take the scanned copy and not even say anything that it's a copy. It's so hard to tell the difference between oroginal and copy natrulization certificate anyways unless they really feel the seal and check the watermakrs and other security features like US agents.
If they still give hard time then i would try to convience them really hard and if that doesnt work may be call the nrna hot line and try to see if anyone could help. Even call home misinstry like khagendra ji was saying , i heard they have a speical desk assiged to help nrns.