I am searching for a panel-mount  20 Amp AC ammeter;

The intent is to show the automotive alternator 3-phase AC current output (i.e. before rectification)

The individual AC phases are to be displayed separately.

The AC Amps range is from 0 to 20Amps AC

Estimated AC output frequency will be between 16Hz and 300HZ

Furthermore, comparable 12VAC Voltmeters are are sought (for the same purpose)

A separate power supply of 5VDC, 12VDC or 220VAC can be made available.

Adaptive external components can also be installed (with your recommended schematic)