The Commissioner of Mental Health and Addiction Services may contract with any public or private agency, including a general hospital and a public health nursing agency, for services for patients or former patients of institutions of the Department of Mental Health and Addiction Services, including, but not limited to, laboratory tests, outpatient clinic services and examinations of, and public health nursing services to, discharged and paroled patients, and may, with the approval of the Commissioner of Administrative Services, contract for the services, on a full-time basis, of professional specialists whose services the Commissioner of Mental Health and Addiction Services is unable to obtain through procedures under chapter 67.