Many years ago I learned about aftermarket parts and their sometimes limited availability. it is the main reason I advise to stay with the stock stuff. Nothing wrong with upgrading the stock components but one can get stung down the road with the aftermarket stuff.
Recently had a customer with a holley commander port EFI that was new but about 20 years ago. Finally got the project running and there is almost no support for it. They did offer to sell him a newer comparable system for about 5K

have you tried flea bay ??