2536771 CAP 4BBL Intake Manifold Port Plug

I am looking for the intake manifold vacuum port plug that was used on the CAP California 273 CI 4bbl intake manifold. If anyone has one lying around or if anyone knows where there might be one with the plug in it Please let me know. Look at the pictures, the first two are of my manifold without the plug, the third is of a manifold that has the plug in it. It is not a standard 3/8" or 1/2" pipe plug, it's some goofy size, and it is not the same size as the vacuum nipple for the performance gauge.
Thanks for your help
Bob

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