The committee has in its power to send for documents, which the committee has done in the past. There's nothing that prohibits any member from putting a motion forward identifying the documents that the committee wishes to receive.
In recent times, that has mostly been done with government departments; however, it's not outside the realm of reason, and I've even seen examples of documents being sought from private individuals or private corporations. Therefore, the committee does have a fairly wide-ranging power within its mandate to send for documents from the government, private individuals, corporations, associations, and so on.