I'm a teacher in a state high school, and one of the occupational hazards is dealing with cheap pens staining my shirt pockets. No matter how you treat them, there is always some of the stain that remains.
If you've ever been involved with teenagers, you'll be aware of how easily influenced they are by appearance. Like it or not, as a teacher, you have to play the part of a "respectable adult" to the hilt if you want to be able to get a class of them to listen to you. :(
As a consequence, I needed to find a way to protect my good work shirts from cheap government-supplied pens, but also in as subtle a manner as possible.
Step 1: The Solution
While hunting for a normal pocket protector (NOBODY sells them anymore!!!), I came across these id pockets.
The were the right size for my pockets, and as a bonus, they were completely invisible inside the shirt.
I place one of these inside the pocket, and make sure to slip the pen into the pocket when I put it inside my shirt.