If I am not mistaken, the battery in question was Rickett's Battery of the 1st Pennsylvania Light Artillery. I have read that there was quite a contest between Rebel and Yankee over the battery guidon. Could this be the flag in question?
These are the units which faced Hays' Brigade
41 NY, 54 NY,58 NY,119 NY, 68 NY, 153 Pa, 17 CT, 25 OH, 75 OH, 107 OH, 1st PA Lt. Arty., Batteries F & G, 1st NY Lt. Arty, Batteries I & L, 5th Maine Battery