La Spiga Bakery in Addison doesn't list cassata as an item, though it is after Easter.
Maybe a trip to the Northeast is in order.
Could bake it yourself?
ITALIAN RUM CAKE
BATTER Mix yellow cake mix, 4-serving pkg vanilla instant pudding, 4 eggs, 1/2 c oil, 1/2 cup dark rum.
GLAZE melt stick of butter, stir in cup granulated sugar, 1/4 cup water. Boil/strir 5 min. Offheat add 1/2 cup dark rum.
ASSEMBLY Pour batter into greased bundt cake pan. Bake 325 deg an hour. Cool.
FINAL invert coooled cake on plate. Fork/prick top. Drizzle glaze evenly over sides/top. Steep cake--there will be a small puddle on the plate - but will absorb after 12 hours. Tent top using toothpicks to elevate saran, or foil in tight seal.