Take my advise or not, it may not be the ideal situation for you, but I think like this. Get a diamond hone of some sort. I bought a 6 in smiths course (yellow) hone for $22.00. Practice on that. Then If you want a little more refined edge, get a fine stone (usually red). Learn to use them. That way if you are "out and about" you will have the skills necessary to put a new edge on your blade or blades. You MIGHT want to try the DMT folding two sided hones. One side is course grit about 300 and the other fine, about 600. The reason I said smiths hones is they are usually cheaper than DMT and I can't really tell a difference.

As I said, this is just my two cents and something for you to think about, nothing more.

Oh and one more thing, for real portability check out the EZE-lap model M diamond rod. It is the choice of a lot of "experts". I have one and like it, Diamond coated steel rod in a brass holder.