Something like this might work..
http://www.medexsupply.com/product_info.php?products_id=3418
I surfed under medical supply (medical finger guard)
Other people here may know of something, but I bet there would not be a great call for something like that made for guitar player.. The cost looked low enough to purchase for experimentation.. 4 sizes, 12 per order.. $6.25 plus shipping..
There were a few other site that I didnot check.. The first checked was right on the money in my mind.
I have tried a sewing thimble but not for protection. More of a one finger slide.. ROTFL
Good luck