Title: Sahaj Boi
Description: As far as I remember this book was published in the mid eighties between 85-87.  It is in Bengali and not by the publisher you mentioned.  It is about teaching Bengali to children in North America.  This book was authored by me for Canadian Bengali School in Bramalea to start with.  
A Note from the Author:
I do not know if this book is available at all, if it is it would be with a few people like Mrittika Inc in New Jersey as they use it on a regular basis as far as I know but they may not have any copies for sale.  I only have my personal copies. Occasionally I have received calls re where to get this book from.

I intend to re-write this book but I cannot afford to pay for the publication hence I am refraining from it.