You can always make an offer and see what happens.
Given that you can't seem to find it anywhere else, and considering the price of similar transmission adapter products, flat-O, Bendtsen, Quick Time, C4 conversion, etc, the prices on eBay seem pretty good. I'd jump on it, before it's gone, if I needed it.
Looks like Speedway only has Che vy to flathead adapters.
Lawrenceville, GA