If I read the statute correctly, ANY of these records can be subpoenaed. §2205 of the presidential records act:
2205. Exceptions to restricted access
Notwithstanding any restrictions on access imposed pursuant to sections 2204 and 2208—
(1) the Archivist and persons employed by the National Archives and Records Administration who are engaged in the performance of normal archival work shall be permitted access to Presidential records in the custody of the Archivist;
(2) subject to any rights, defenses, or privileges which the United States or any agency or person may invoke, Presidential records shall be made available—
(A) pursuant to subpoena or other judicial process issued by a court of competent jurisdiction for the purposes of any civil or criminal investigation or proceeding;
(B) to an incumbent President if such records contain information that is needed for the conduct of current business of the incumbent President’s office and that is not otherwise available; and
(C) to either House of Congress, or, to the extent of matter within its jurisdiction, to any committee or subcommittee thereof if such records contain information that is needed for the conduct of its business and that is not otherwise available; and
(3) the Presidential records of a former President shall be available to such former President or the former President’s designated representative.
...ANY of these records can be subpoenaed.
Actually, they don't need a subpoena at all.
Neither (2)(B) nor (2)(C) make mention of a subpoena.
...not otherwise available...
No copies? No problem.
Or is he going to say 'no' to a Senate committee or subcommittee request?