I recently learned of another script used for writing the Rai language of Sikkim. It was brought to my attention by Bijay Bantawa. It appears to be a revision of the 'Khambu Rai' script I wrote about earlier.
Here are the consonant letters for Kirat Rai with their Devanagari correspondences:
I will soon submit a document introducing this script to the Unicode Technical Committee. Any information about this script is welcome.