This is a rundown of most of what's out there:
Tools for Measuring Case Neckwalls
If I were you, I'd stay away from thickness measurements with indicators though.
Something the article also missed is that you must have a means of setting depth from the case mouth, for the inner contact. Otherwise, on unturned brass, your measurements would not be at a consistent point around the neck.
With the Sinclair models you can drop washers over the anvil as a case mouth stop.
These things aren't cheap. But if you want straight brass, or tighter neck tolerances, it ain't gonna happen by chance. To find the best brass, it has to be measured with precision.