Hmmm, have you tried to go through the online (PC) Xbox marketplace?
I'm still finding it, but mine is on the Belgian/Dutch marketplace.
But clicking it will maybe take you to the italian one?
If not, try going on www.xbox.com
, search "third strike" and see if it's still available for you.
If so, you can activate the download from there with your account, and when you turn on your xbox, it should start downloading.