If you are required to submit a certified copy, you obtain the document by going to the court clerk at the courthouse where the charges originated. Give the clierk the name and the case number and they will be able to give you a certified copy of the disposition.
This answer is provided for informational purposes only. Actual legal advice can only be provided in an office consultation by an attorney licensed in your jurisdiction, with experience in the area of law in which your concern lies.
Any official copy of court documents should contain the official stamp of the court. If you need this document to ensure a smooth re-entry into the country, I would suggest that, prior to leaving the country, you discuss any and all immigration issues with a qualified immigration lawyer. It's better to make sure you have everything you need and in order before leaving and further make sure you understand your situation and all the issues.
You can obtain a certified copy of the disposition from the clerk's office where the case was pending. The certified copy will be stamped by the clerk. Hope this helps and good luck.