Although most of my sharpening is using a Sharpmaker, I have a couple collapsible and folding diamond rod files (e.g. from Smith's and DMT that could probably fit in a pocket if needed. Generally speaking I strop my folders on my jeans or the back of my leather belt if I do a little work (I don't know if it does anything). I also heard that you can use the bottom of a coffee mug or even the edge of your cars windshield (I've tried neither). I've seen SAK aftermarket leather sheaths that come with a mini knife steel too.