Diamond sharpening cards are great for a pocket or a pack. Slim, simple, affordable, durable. Only issue is they are hard to hold onto.
Add hook velcro to the back though..

And now you can stick it to the loop field on your bag and use it..

Or create a loop of loop and you have a packable handle..

This creates lots of ways to attach or hold onto it while sharpening. No nicked fingers.