Sri Pamchanan was the chief disciple of Sri LAhIrI mahAshaya.
Very well known for his geeta commentary.
I would like to know about all books penned by him and if any of these available online as pdf version
It seems you can order books by him and on him from this website:
(Shipping to India though...)
These books are available online : https://www.amazon.in/Books-Panchanan-Bhattacharya/s?ie=UTF8&page=1&rh=n%3A976389031%2Cp_27%3APanchanan%20Bhattacharya
I could not get the list of all His books.I shall search for His bengali books and update.But probably these if any are not yet been translated.