Effective January 1, 1978, the county commission of each county wherein the provisions of this article are applicable, shall purchase a professional liability insurance policy covering all deputy sheriffs subject to this article, which policy shall provide for minimum coverage of $50,000 for each person injured or damaged in each occurrence and $100,000 total coverage for each occurrence. Every such policy shall be written on an occurrence basis only. Such policy shall be paid for out of the county General Revenue Fund. The county commission may purchase additional coverage and, as to such additional coverage, may pay all or any part of the premiums as it and its sole discretion deems appropriate or, as to such additional coverage may require contributions in whole or in part from the sheriff and from the deputy sheriffs required to be covered by such insurance. Such additional insurance may not be purchased and the premiums in whole or in part paid by such deputies except with the consent of the majority of the deputies to be covered thereby.