Bro,
You would have to tell me what exactly a KMG or Hardcore needs! LOL!
As stated, you can put your own axle in ANY contact wheel, with the correct diameter shaft, made to work for your grinder...
You'd have to turn a shaft, or find one for sale..
Also, you can change bearings in the wheel to fit your axle, which would be fairly cheap, if you go to Applied Industrial Tech, and order the bearings with the correct inside diameter...