The leather pumps, like were used by Carter, last virtually indefinitely, as you have determined.
We still had pumps as late as 2010, but have now run out, probable that your carb was rebuilt using a leather pump.
As the pump used in the 684s is unique to the 684s, there is insufficient demand to do a major run of the pumps, so we have to make each one by hand.
Jerry - the YH's used by Nash are almost as difficult to find as the original Corvette, while the Dearborn variety is somewhat more common.
Jon.
