I'll tell you what to look for, because I spent three hours tearing up the basement, looking for something I stumbled across a few weeks ago. Now that I need it, I can't find it. (I found some other stuff, though, and got distracted from the rest of the search.)
You want something in the $7-$8 price range called a diamond rod sharpener. Here is a picture of one by Buck, but there are other brands too. Stay away from ceramic sticks for now.
They're usually round, with one flat side. With the sharpener extended, you gently move it up and down the edge of the knife, trying to match the original sharpened area. Keep a couple of drops of water on the blade, because diamond sharpeners work best with water to flush away the microscopic shavings.
When you use a diamond sharper, you must always use a gentle touch. Diamond will sharpen the toughest steel, but it's always best to go slowly.
If you had a knife with a regular edge, rather than a one-sided grind, there are plenty of simple V-type sharpeners that will work. But with the blade you have, you have to use a rod that will sharpen only that one side.