The Gator GKPE-61 TSA hard case works well for the S-12 harp guitar.  Its molded plastic shell is ultra durable and the partially recessed lockable hinges add elegant functionality to this case.  If you are looking to do any air traveling with your harp guitar, this case is the recommended choice.  Retail is around $350 online and is well worth it for the security and insurance that your instrument won’t get damaged by the air lines baggage handlers.  To purchase, search online at Amazon or Sweetwater, and you may sometimes find them marked down or used on eBay.