If you still want to hunt for user-created X5D Kontakt libraries:
(the free Kontakt Player often runs these in "Demo Mode" for only 15 minutes). korg x5d kontakt sample library free
Start by searching Musical Artifacts for "Korg X5D" and download the .sf2 files. Loading those into Kontakt is your best bet for a free, authentic library. If you still want to hunt for user-created