We're in the same boat; there is no public source for identifying the beneficial owners of an entity or verifying beneficial ownership as self reported by individuals connected to those entities. If we collect beneficial ownership information we are just writing down what people tell us, nothing more.
Ignorant of corporate structure in Canada, I'll say that in the U.S. an attestation would probably be the most effective if it were executed by an officer of the entity who was named in the entity's most recently required filing with the state of its incorporation. It would also be executed under penalties of perjury; i.e. lying would be a crime. Neither requirement could be said to be of any immediate value to the bank, but both would be helpful to law enforcement should the little darlings choose to lie.
The model form contained in the proposal linked above contains neither of these features, but it has been roundly criticized for those and other shortcomings.
In this world you must be oh so smart or oh so pleasant. Well, for years I was smart. I recommend pleasant.