Thought I would share this as I didn't see any posts about it.
My DW gave me a new Fisher Space Pen for Christmas. It's an updated design with key ring loop and secure snugly-fitting cap.
I have been EDCing it for almost a month and it is staying firmly attached.
I was very frustrated with the older "bullet" style ones as my last three were lost due to the clip slipping off.
Pic is here to give an idea of size relative to car key:
Regards,
Buckeye