I wish I had my notes and books with me to go over my list of captured flag at Gettysburg. But just off the top of my head, these Union regiments lost flags: 149th PA, 150th PA, 142nd PA, 11th US Regulars, 3rd Maine, Reynold's Corps flag or some type of HQ Flag (Colonel Perrin) wrote that his men captured it, along with a "Large flag of the 149th PA, battery flag and a guidon". Gordon's men captured a few flags from the 11th Corps. Hay's men took Four flags. Many more out there.
Thank you for the outstanding post on the 11th US. Regulars!
Shawn Prouty