For my high school senior project back in '04 I retrofitted the internals from a classic VL 2000 into a much smaller (50-60 round I think, it was a no name brand). It only took me about $25 and 3 or so hours to build. It ended up coming out really well and worked great, the agitator just barely sticks into the hopper and kind of "pokes" the balls rather than stirs them. I have PDF files on my old computer with blueprints I'll try to find it.
Anyone remember those old Zap "mach" something-or-other hoppers? They were really light, but agitated like crap. I wonder if they'd be good for making a small/light setup.