Is your key black or grey? If it's black then it should be a master, and therefore you'll just be able to get another key off ebay, get it cut and program it yourself using the guide on here.
The sportcross remote is supposed to only have 2 buttons, it doesn't have a separate boot button as the boot unlocks with the rest of the car - but having said that I see no reason why a 3 button IS200 key shouldn't work if you can't find the 2 button key.