I realize I'm months late, buuuuuuuuuut...I don't think you're really going to find anything that's going to match up to the taste of a real tiramisu.
Tiramisu is my absolute FAVORITE dessert of all time, so I treat myself every once in a while (maybe 3 times a year?) and split a slice w/ my mom at Olive Garden. They also have tiramisu in a dessert shooter there, so it's just the perfect size to indulge but not overdo it.
Maybe not the best advice, mind you, but my advice would be to indulge in the real thing once in a while.
1st goal - 10% of body weight lost - MET 06/21/10
2nd goal - 100 lbs lost
3rd goal - 180 lbs!!!