I bought a couple of those off a guy who used to sell them on eBay, but he has since passed away. He also used to sell them to Firebird central which is why I believe they are not available anymore.
A member (wwblue69) here sells some I believe that might fit.
He says the 1.375 fits inside the formula steering wheel horn cap
Here is the link to his stuff he is selling https://firstgenfirebird.org/forums...t-gen-wings-down-emblems.html#Post324491
Here is his contact info: steele.pontiac@gmail.com. or cell is 567-259-8510 His name is nick