See if you can find A distributor for Spaenaur. Their part number for the Pantera fastener is 110-062 available in Zinc plating [full retail for these is 10.69ea, sold in boxes of 10, can't complain about price] I did not look-up the base/plate number but I remember seeing it in the catalogue. There was also another supplier Southco, but I didn't do much research in their cataloque. Hope this helps. If you can't find drop me a PM and I will go to the store.
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