end client letter not issued by client

i got a rfe for my visa application 2017. i have all the documents except end client letter.They never issued such letters to any of the employees.Neither i can get MSA or SOW documents.

in some other website,i read that i can attach the mail from the client stating that they don’t provide such documents.But i don’t have the rights to write this kind of mail to my client.My manager deals with them.And he is hesitant to do it.

kindly suggest me what can i do?