Looks like Scuderia doesn't have them in stock, but can order them for you.
The problem you have is that you can program the door lock/unlock with the ThinkDiag, but you can't program the car start portion.
To program the ability to start the car, you need two already working keys. The procedure is as follows...
1) Put one working key in the car and start the car. Immediately remove the key.
2) Quickly put in the 2nd working key and start the car. Immedaitely remove the key.
3) Put in the new key, and if you've done it all fast enough, the system should learn the new key.
I used this procedure to learn a new crystal key for my '09 Vantage in combination with the ThinkDiag to program the door unlock, but I already had three valet keys that came with my car.
As far as I know, without two working keys, your only real option is to go somewhere that has an Aston computer.