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

We use the Army ground guiding signals. I figure the Army has decades of experience moving around heavy expensive equipment in stressful situations. Like anything else, parking lot practice coms in handy, of course.

There is a video here: https://m.youtube.com/watch?v=C_7MedRrACM

The Army Field Manual section is here: http://armypubs.army.mil/doctrine/DR_pubs/dr_a/pdf/fm21_60.pdf