Go to any auto parts store and ask for a spark plug boot. Make sure you get the metal contact that goes inside it.
I've said this so many times, I can't count. The kit supplied plug boot is the weakest link in the kit. It's the first thing I throw away when I open the box. It's too heavy, it doesn't allow for good electrical contact with the plug and, they fall apart. Throw what's left of yours in the trash and go get a real plug boot.
Do not order a replacement because you'll be right back to square one with a boot like the one that came with your engine.
The kit boot requires that you remove the cap at the top of the plug and it relies on the threaded portion under that cap for contact. That's just plain stupid. An automotive quality plug boot will let you use the plug, cap still installed and will give you much more contact area for the high voltage current of the ignition system.
All newer kits come with the plug wire superglued into the CDI. You'll have to dig around the wire to get it out but be careful and do not damage the threaded contact that screws into the core (conductor) of the wire.
They're always too short, but the kit wire is better than what you'll find at most auto parts stores because it is a copper, or at least a metallic core wire as opposed to resistance wire that most auto parts stores sell today.
Tom