here is a site with a bunch of italian dessert recipes. Some of them look really good. At the bottom of the tiramisu recipe, it says:
" *Note: If mascarpone cheese is unavailable, blend 1 lb. cream cheese with1/2 cup heavy cream. That might be your solution.
I would think that you should be able to get the marscapone in a deli or specialty store. I've bought it in the specialty cheese section of my local supermarket.