I can't find it!
Here's what I do......if I absolutely have to!
Cut a thin strip of tape,using a good straight edge,the same width as the widest part of the spiral.Make sure its a bit longer than the total length you need.
Now cut this strip into two diagonally along its length.
You will have two long thin 'wedges' to use as a mask (and a spare!).
Start one from the thin end at the top and work it around the spinner towards the bottom.
You may need to trim a bit of excess.
It is a fiddle and you will have to make some adjustments but it can be done. Remember if you mess it up it's just a bit of tape,no harm done. I've NEVER got it right first time!
Cheers
Steve
Edit:
Forgot an imortant point. Becase you've cut the tape on a diagonal one edge is longer than the other and should be on the bottom,that is towards the spinner base plate.