If you just replace the stalk, the LED won't flash unless you get the BCU reprogrammed to add alarm function.
You can buy the stalk from BMW/MINI dealer or sometimes they appear on ebay but check the part number required @
RealOEM.com Online BMW Parts Catalog.
Not sure if the alarm LED wiring is always fitted, so you may have to run cable from the BCU to the stalk as well.
Hope this helps.
If you need any more info, just ask.