Where can I buy a " 1/2" NPT female x 1/2" ID hose barb " with a true 1/2" inside diameter? My Chugger pump requires a minimum of 1/2" feed to eliminate cavitation.
Hose barbs in that size range seem to usually have a 1/16th inch wall thickness, so the bore would be 0.125" smaller than the corresponding hose. In other words, to get a minimum 1/2" ID in a hose barb, you'll need a 5/8" barb, and change your hoses to 5/8 as well.
To answer the question above, try a hydraulic supply shop, Grainger, truck repair, etc. Bring a lot of cash because, although they can get what you want, in stainless, they will also make the stuff at your local homebrew shop look like its almost free.
Another way to solve the problem would be to lower the pump relative to the liguid (so the internal pressure is higher) or restrict the outlet so flow is reduced.