The gooseneck mic we are using is the Clearcom GM-9.
You recommend mics such as the Telex / RTS MCP-90 series are suitable - and the GM-9 appears to be 1:1 compatible ie.:
phantom-powered "back-electret"; threaded TRS male connector; phantom powered voltage range of 1.5 to 9 VDC.
BUT - we

* Is there a board level switch / jumper for bias V on / off between dynamic & electret maybe ?
* Any other ideas ... please ?