Big,
Found this link in the old forums......may be of help to you.
Don't know the age of your bike but it may be an issue of 2 different styles?
BTW, I've got a spare sidestand I had planned on having shortened when I lowered my bike but found out I didn't have to.
If you are interested let me know. I don't know what Triumph gets for a new one. Maybe yours is under warranty?
Link