Cliar has a website
I have e-mail addresses for two band members, and they've given me info in the past - but if they've recorded the song the lyrics might be included with the album

Anyway, there's a website with songs of Donnchadh Bàn Mac an t-Saoir, Òrain Dhonnachaidh Bhàin which includes a version of Cumha Choire A' Cheathaich, about 20 verses long. Oran Choire a' Cheathaich is included as well.