Amazon Kindle now has the title "Let Yourself Be Led by the Immaculate", written by Maximilian Kolbe, translated from the polish by a Dominican brother. Most of his works are available in Polish and (in translation) in Russian... but sadly have not yet been translated into English extensively. I hope that after the canonization of Pope John Paul II, a renewed interest in this "Saint of the troubled 20th Century" will occurr, but it just hasn't happened yet. He is a truly remarkable man and a wonderful Saint for anyone to follow and learn from.
While not directly related to your quest for his writings, I wondered if you know about the National Shrine to Saint Maximilian Kolbe? Their contact email is: firstname.lastname@example.org and they also have phone numbers, but I have found that sending an email asking questions or for help is usually fruitful. If you send them a question, I am sure someone could help you out and direct you to the proper documents and whether or not they can be obtained in digital or written format.
The title in the Kindle Store:Let Yourself Be Led by the Immaculate Kindle Edition by St. Maximilian Kolbe.