secondary diaphragm

Hello, Can anyone point me towards a source for the vacuum diaphragm that operates the secondaries on a 20r Carb? I'm having a really hard time finding one. If no source exists is there a way to repair these old diaphragms? I have a sneaking suspicion that mine failed recently. Have not...

I've so far been unable to get my secondary to open.. I rebuilt my carb ~1,500 miles ago, did a good job, made sure all the vacuum passageways were open, and of course installed a new secondary diaphragm. However, I found that the secondary was not opening beyond the minor amount initiated by...