Hi Jon -
The Articles of Agreement in Regard to the Surrender of the Army of Northern Virginia under Gen. Robert E. Lee, April 10, 1865 has been digitized and can be found here: Our Documents - Articles of Agreement Relating to the Surrender of the Army of Northern Virginia (1865)
Additionally, the Archives Library Information Center, at Archives II in College Park, MD, has a set of volumes relating to the Official Records of the Union and Confederate Armies.
There are two microfilm reels that might help if you know the units that were there. These are M594, Compiled Records Showing Service of Military Units in Volunteer Union Organizations (225 rolls), and M861, Compiled Records Showing Service of Military Units in Confederate Organizations (74 rolls).
To purchase, or see where NARA has copies of these microfilm rolls, please see these two links:
Finally, you might also check out the Library of Congress. It appears they have a significant manuscript collection that references the surrender at Appomattox. They can be found here: Civil War Manuscripts
Best of luck in hunting down what you're looking for!
Thanks very much, Ann. I will start looking through these materials. Best regards, Jon.