Depends on your willingness to use console commands or not.
Alternative: Conquer Poland, Pomerania or Avaria
Conquer one of these kingdoms, make it your primary, destroy Moravia, create Bohemia, make Bohemia your primary, destroy the other kingdom. Silly and might not be possible in CK2+, as many titles have the requirement "Rank is lower than King". I'm not sure about Moravia and Bohemia.
Alternative: Lose the kingdom of Moravia
I've never done this, so I'm not quite sure of how you would go about it. If it's a titular kingdom, there might be some problems; I've never seen a Titular Title being usurped. Potentially give away all lands de jour Moravia to some imbecile, wait for him to usurp the title and reconquer your lands when the truce is over; do not press claims so you regain the title, remove Moravia from existence.
Alternative: Use console commands
Yes, it's cheating and breaks immersion, but it's a quick way to get rid of Moravia and really, you could just RP around it.
Giving yourself Moravia via console commands:
charinfo (reveals character IDs)
give_title k_bohemia [character ID] (remove the brackets, enter the ID, usually something along these lines: 1000XXYYZZ)
More info about console commands can be found
here.
EDIT
Come to thing about it, giving away the lands of Moravia is most likely not possible unless you grant it to and infidel or heretic. You can't grant Independence to vassals of the same religion, who are de jour to your primary title.
Might be possible if you find yourself a infidel or heretic, however, I'm not 100% sure.
