Re-Creating a trimmed surface for Lunchbox paneling

Hey guys,
The end goal is to triangular panel this surface with grasshopper but I’m running into issues because it’s a trimmed surface. I’ve had a look at other posts with similar issues but they didn’t seem to help because my surface is shaped quite differently.

I guess I’m looking for advice on either how to best re-create this surface so it’s no longer a trimmed surface (whether through GH or Rhino), or how I could input this differently into GH (keeping in mind the end goal is to panel)

Untitled.3dm (338.0 KB)

Cheers guys (63.2 KB)

Have a look at the attached.
From my knowledge I can only try to approximate the original surface as close as possible,
but never identical.
You can adjust the tolerance by playing with the slider, and also the original number of contour curves.