Which brand & model of walkie talkies for my "spotter?"

Any of the FRS radio work just fine. It you get one with PRIVATE LINE on them it might block other users from being heard on your unit.

We also stumbled onto using an old multi-telephone setup. We had an old four handset model not being used. Just plug it into 120VAC or wire up for 12VDC using the proper adapter. The handsets work great in intercom mode... Does not need to be connected to a working telephone connection.

Roy Ken