Honor Guardsmen and Reservists Act - Directs the Secretary of Veterans Affairs (VA) to make available for purchase a memorial headstone or marker for the marked or unmarked grave of: (1) an individual who performed inactive duty training or active duty for training as a member of a reserve component, but did not serve on active duty and is not otherwise ineligible for a memorial headstone or marker on account of the nature of the individual's separation from the Armed Forces or other cause; or (2) such an individual whose remains are unavailable.