J. Michelle Watts book The Quilted Cross doesn't have any Jerusalem Crosses; however, it does have some cool crosses that are similar... the Cross Crosslet, for example.
Does your nephew play Dungeons and Dragons? Is he a Paladin by any chance?
And how funny/timely, our bulletin from All Saints' Day had a really neat cross on it, so cool that Mom and I are both appliqueing it... From an enlargement of the bulletin with some improvements to make it easier to applique. It's the first thing I might embellish.