Hello Walt
I think this might fit your criteria admirably:
There is a very old trick called HALF & HALF utilizing two cardboard easels with a hook on each. One easel is red, the other black. Neither easel is gimmicked.
A jumbo Bicycle deck with a hole in the center lower quarter of each card is introduced and shown to the audience to be a true mixture of red and black cards (no dupes, stacks etc.)
The cards are honestly mixed and then one at-a-time removed from the top of the deck and displayed back facing the audience. (An audience member could have done the mixing.)
A random spectator calls out red or black. The card so designated is hung on the hook/easel of the appropriate color. This is continued for as long as you like, with no secretive counting, tricky handling or anything like that.
For the grand finale' the cards on the red easel are removed--staying in sight the entire time-- and shown to be all red cards. The same procedure is followed with the cards on the black easel being all black. No switches.
Not bad for an oldie, but goodie.
Julie