Bengali ISIS Keyboard missing characters

The Bengali phonetic ISIS keyboard (developed by Prof Gautam Sengupta, free with BengaliKeyman) lacks certain characters which appear in many Bengali words:
(I list below the unicode names and values):
VOCALIC R - 098B
SIGN VOCALIC R - 09C3
KHANDA TA - 09CE
And several of the dotted letters:
YYA - 09DF
RRA - 09DC
RHA - 09DD
The ISIS Keyboard produces lookalike characters for these last three, made up of the undotted version of each character (YA, DDA, DDHA) plus a separate NUKTA (dot = unicode 09BC) - but this is unacceptable for many purposes. I would like to modify the keyboard to solve these issues.

The ISIS keyboards do not currently have source available. I am writing to the author to see if he is able to make source available.

Thanks for your prompt response! Would be great to get this keyboard fully
functional. I will wait. James LW

James, We were never able to get permission to move the ISIS keyboards to the MIT license.

However, recently someone has created another Bengali keyboard that seems to have all the characters you were requesting. You can download it here:
https://keyman.com/keyboards/itrans_bengali
and the online help file:
https://help.keyman.com/keyboard/itrans_bengali

If this suits your needs, can you let me know and we’ll close the issue about updating the ISIS keyboard?