If I remember correctly, the flag Kennedy presented to Ireland was the green "Tiffany" presentation color (late '62?) for the 69th NY. I've never heard for sure if this was the only flag he presented or not.
On a side note, if you'd like to find a rare Irish unit flag, try the snipe hunt that is searching for the colors of the "San Patricio" battalion during the Mexican War.
Josh Bucchioni