Try flights from Iqaluit, YFB, with First Air or Canadian North; flights may go via Nuuk.

Alternately, and this is rather a long way round, fly with NY, Air Iceland (the domestic sister of FI, Icelandair) from RKV to Tasillaq then to THU via Kangerlussuaq with Air Greenland.

I flew with NY to Tasillaq a few years ago in a Fokker-100, and it was one of the best flights I've ever made. The sight of the icebergs in the sea as we approached the coast of Greenland was amazing, and things just got better after landing and the 'copter trip to Kulusuk.

Greenland was :-::-::-::-: fantastic in all ways, and I would go back in a microsecond. I hope you get to THU and enjoy your visit as much as I did mine.