I got these from AMS Obsolete, the former Mitchell Motor Parts. They have a couple other businesses under their umbrella, including Herb's parts and Charger Specialties. I got them off Ebay, didn't see them on their webpage. There aren't any more listed. I may have gotten the last of them. Or call them and ask. I've had good luck with them on the phone. NEW Replacement 1969 Plymouth Barracuda 'Cuda Hood Turn Signal Wire Clip Set | eBay AMS Obsolete Home Page (amsnos.com)
Classic Industries lists them as out of stock/obsolete.
I don't know if they were used on later A-Bodies. I can't find a picture or part number anywhere in the manuals. From what I can tell, they were used to hold the hood mounted turn signal wires to the firewall and underside of the hood.