All you need to do its start with , " I solemnly and sincerely declare that ,
My full name is .......
I was born in xxx on xxx xxxx
My mothers name is xxxxx. Dob
My fathers name is xxxx dob
I have enquires with the xxxx authorities and to the best of my knowledge and belief, no record of my birth exists.
This declaration made by my at xxxx on xxxx by virtue of the Oaths and Declaration Act
Signed
Witnessed. ( witness details)
You don't need a notary, just a justice of the peace. It is you rdeclaration, not the witnessing persons, so they should have no involvement with the content.
You don't need anything for your EOI , but will need to submit a declaration if you don't have a birth certificate when it comes to your application.