For me there are two ways :
1. sand off the black part to reveal the wood (I guess this is necessary to make it legal), then take off the curved part of the cork (the distance to be left towards the handle is up to you), in this way the brand and type of the rubber will still be there (I guess this is also necessary to make it legal).
2. Buy a J-pen twiddler, where the forehand side is exactly the same with the backhand side (example : Violin J-RH or Violin-PH).