good question- I have never seen one. I have shot two fingers for over 50 years.
I have found the best way to shoot a whole lot is to shoot two arrows and rove; and that way my fingers get a minutes rest between shots.
Lately I practiced shooting 6 arrows with a friend for weeks- at a target face and pulling the arrows and shooting at another target.
I painfully I wore out my 'under the arrow finger'; which takes the primary force from the string.
I have in the past dealt with this by taking a Damascus glove; I cut off the finger tips on them; and then slip in between the layers of leather cut and measured piece of the connective plastic from 6 packs of pop. (The stuff sea birds try to eat). Its just the right consistency and saves my finger from wear and tear.
I am not sure why I started shooting two fingers- I guess because I had to shoot my bow quick - before my brother killed me with his Roy Rogers pistols.
I have instructed kids on shooting bows; and not told them how many fingers to use and how to hold the string; and it almost takes on the appearance of instinct controlling them.
Some will use three fingers; some two; some use their thumb and one kid even stared at his thumb like something was missing ( like a thumb ring).
If we could trace down the tribal origin of two finger shooters - maybe we could find out how they dealt with it