Think yer prolly referring to the spark plug cap?
If so - yeah, it's a total POS and needs be replaced, even if you could put it back together - it'd just fail again. Fortunately, it's simply screwed on - there's what looks a heck of a lot like a wood screw in it, simply hold the wire itself and twist the cap assembly counterclockwise to unscrew it. It may seem a weird way to connect it but it's common on many small engines and quality replacement caps are easy to find. Some larger engines use a lil sharp pin inside and a tight press fit - so check what yer buyin'
An auto parts place might be limited to sets of 4, 6, and 8 for somewhat obvious reasons - check yer local motorcycle shop and lawnmower repair centers for just one. The wire itself is surprisingly good with a generous amount of copper wire in it - so I'd keep that on there if ya can (it unscrews from the CDI "black box" as well if you do need to change it).