Mo. Rev. Stat. § 180.070: Librarian may procure books.

When there shall be a want of continuity in any of the series of acts, journals or other books required to be placed in the library, it shall be the duty of the librarian to open a correspondence with the proper person, in order to obtain those which are wanting, and if they cannot otherwise be procured, he shall purchase the same and place them in the library.