WTB 67 Tri-Power PVC vent tube manifold fitting

[Chicken Coupe]

Hoping someone has available or can possibly direct me to a source. 67 427/435 tri-power manifold, pass side of manifold, below center carb, there are 2 ports: Top one normally has a press fit tube that is used for the hose connection to the PVC hose going to pass. side VC/PVC valve. (Lower one is commonly plugged with a "freeze plug") Or if anyone knows if it is a common size hole that I can use a common part to fix (i.e.-small piece of steel brake tube). Thanks in Advance, Fred