Brian's photo problems - jaggies

OK, simple problem. One of the next of my "Plant-Watcher" pages will be on the horse-chestnut, being the tree of Tochigi-ken. I want to include a picture from when I talked to the kids in Aki's class, of me "teaching" someone how to play conkers. Have scanned APS frame (wow - grain!) from teacher's camera, and particularly with the grain, I want to use a quite small version. Trouble is, the string on the conker ends up just 1 pixel thick, and this results in horrible jaggies. Here's a little bit of the original scan (left) showing that the string is resolved quite clearly, then on the right the result of ordinary resizing using Paint Shop Pro, with a little enlargement of the string.

Does anyone have any helpful ideas on any way of fudging better string?