I checked in one of my old catalogs, A3 is the Private, U.S. Infantry 1776-83 James Payette (in hunters garb) and A5 is the Private, U.S. Infantry 1776-83 Theodor Stobel.
I have the A5 but when I opened my old kit, I found the base is missing in my kit as well. I'll look around my spare parts and such. Sorry.
Kevin D.