See what brand the actual carrier is and check with them. I believe different companies used different bearings. Or get the part numbers off the bearing themselves.
So what's that tell ya?
Post some pics of this abortion.
LINK TO NEW PLUG CAPS---GET YA SOME http://farmandsandtoys.com/ocart2/ATVs/yamaha/banshee/spark-plug-cap-klg.html?filter=52