Honor Guardsmen and Reservists Act This bill directs the Department 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 for at least six years as a member of a National Guard or 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. Such a headstone or marker may be purchased under this subsection by: (1) the individual; (2) the surviving spouse, child, sibling, or parent of the individual; or (3) an individual other than the next of kin, as determined by the VA.