Go to any paint body shop supply and ask them for clear vinyl protective material...they come in sheets so cut it to the shape needed.
On my 09, I used some of that material to protect the edge on my rear hugger that kept being chipped and have to do that again on my new bike actualy.
It actually came from a Toyota Tundra pick up that is located at the bottom of the bed wheel housing. lol
It's a triangular piece and I only cut a small strip out of it but it's big enough to shape a patch for your knee rubbing issues.