So thanks to WaitingFor_22 leading the way, I was able to find what I think is the sample source of the end of Kaini Industries: Music of the Jívaro of Ecuador (1973). It's the combination of two tracks Calling an Enemy's Arutam Soul (Log Signal Drum Solo) and Song of Kungi, the Flute Bird (Flute Solo). They're both lowered in pitch and chopped up/sampled, but here's a close representation.
And here is the track along with the Kaini Industries sample for comparison.
(I'll update Bocpages I think on this one tomorrow).
