The Secretary is authorized to enter into agreements with the owners of property in proximity to but outside the boundary of the park on which historic monuments and tablets commemorating the Battle of Gettysburg have been erected on or before January 1, 1990. The Secretary may make funds available, subject to appropriations, for the maintenance, protection, and interpretation of such monuments and tablets pursuant to such agreements. In addition, within the area depicted as the “Gettysburg Battlefield Historic District” on the map referred to in section 430g-4(a) of this title, or in proximity thereto, the Secretary may, with the consent of the owner, acquire, by donation, purchase, or exchange, lands and interests comprising such monuments and tablets together with lands and interests necessary to provide adequate public access thereto.