Have a look at this website.
http://www.akwbooks.com/
I am a fan of Enders game too. This is a small ebook publishing website. There is a book for sale called "The Fighter King". I think you would like it. There are three books in the series so far and it is chronologically first. I am part way through it and it is excellent.
Here is the blurb.
Oliver Lincoln III is a walking contradiction – he sells combat fighters for his dad’s defense plant, but he is a dedicated pacifist.
During a sales trip to the Sirian Confederacy, Oliver’s sister, a holonews reporter, tells him a disturbing secret. When his sister is later murdered by the Sirian secret police, the KK, it doesn’t take Oliver long to put the squares together — Sirius is about to invade a peaceful world, using the combat fighters he sold them!
Oliver can’t prevent the invasion, but in a desperate race against time he travels to Vega 3, hoping to arm them with Lincoln fighters so they can at least defend themselves. But the timetable is shorter than he thought, and he finds himself trapped in a global war with a difficult choice to make.
The Fighter King is a novel about the clash of civilization, personal choices, and coming of age. Before The Fighter Queen, there was The Fighter King. It all starts here.