You may file a Stipulated Order Amending Divorce Judgment with the court. Indicate the change that you are seeking, indicate that nothing else about the original order should be changed, indicate that the parties are in agreement and that no hearing is necessary, make sure you both sign it.
Good luck with your situation. If you believe you may wish to hire a lawyer to help, please feel free to contact me. DISCLAIMER I am a lawyer, but I am not your lawyer unless you come to my office and we sign an engagement agreement. The answer provided here is for general purposes only, and does not presume to correctly address your particular circumstances. My answering this question does not create an attorney/client relationship.