Here's how to add add extra comfort & grip to your stock Samsung S Pen.
Step 1: Find a Spare Pen That Has a Nice Rubber Grip and Remove It.
The tips can usually be screwed out. Do that.
Then, you might have to apply some force and break the plastic body of the pen in order for the grip to come loose.
Step 2: Add Some Cloth or Other Material to Use As Filler Between the Grip and the Pen.
Step 3: Profit?
Enjoy your nice comfortable pen! No need to buy a new one :)