Buy yourself a new universal set and don't worry about Sig. The Sig replacement is not exactly the same as the ARF version uses anyway.

I'm putting a Great Planes mount in my Four Star 60 because the one that came with it has cold check seams all over it. I knocked out the blind nuts on mine and installed new ones in the correct positions that were not metric. 6-32. I used a piece of threaded rod stuck through the holes from the front to draw the new blind nuts into place.

Enjoy,

Jim