New or used on eBay, which is somewhat iffy for an uncommon item. Or tons of footwork/phonework to search servicers across the country who may have the item on-hand or a junked oven from which a set can be harvested.

If you have the hinge part number, you can google it, e.g. "Dacor oven 123456", and any of the many online resellers of parts might have it. To find the hinge part number, google the Dacor model number of your range. You can usually find the parts diagram online, even for old models.