There are actually two guys from Freeman, Missouri, a small town south of Kansas City, selling watch bands on eBay. They are the "American Pickers" of watch bands. Tony is very knowledgeable on the subject and gave me some insight into history of makers of bands often seen on Accutron watches. From what he had to say, I can see the justification for the price difference between those made with ordinary straight or curved end links and those that were made to fit the "B" case Accutrons exactly. Many large coffin link bands made in Hong Kong and sold on eBay to fit the Astronaut have end links that protrude too much towards the case for the spring pin to install. Tony told me that those that were original to the Astronauts had curved end links much like the bullet bands with tabs that angled down to fit under the case. Tony currently has a band listed (251202267243) for $320.99 that he believes would fit an Astronaut but he doesn't own an Astronaut to check the fit. As knowledgeable as he is, I have my doubts only because I have never seen one of the curved end coffin link bands on an Astronaut and good photos of the end links don't exist. The coffin link variety seem to have been common on early Astronauts as seen in Bulova advertising of the day but were phased out in favor of the bullet type after just a year or two. I am almost certain that my M4 Astronaut came with a large coffin link band but did the original have straight or curved ends? $320.99 is a lot to spend without knowing more.
If any of you reading this have a U.S. made large coffin link band made by Kreisler Stelux that has the curved ends, it would be helpful to see some photos showing how if fits the Astronaut "B" case.