Is there somewhere I can read the final chapters to "Ender's Game"? Card said that he rewrote the last couple of chapters to mesh better with his later books and also do Ender justice. Where can I get a copy of these chapters?
You can not find the replacement chapter anywhere. The afterword for Ender in Exile said that the revised chapter 15 would be sent out to the Intergalactic Medicine Show subscribers, but this never happened.
The back issue content of IGMS is no longer paywalled and you can view everything online. You'll find a few writings related to Ender's Game, but not the revised chapter Card promised. It was also never included in Uncle Orson on the Fly, Card's other paid subscription service.
The revised edition of Ender's Game kept on being delayed as Card expanded the scope of his revision, trying to bring it in line with all the other books, trying to use it as a way to include his unused film script, and then wanting to wait for the prequel books to finish. The last update is that Card has said that the Ender's Game Alive audioplay adaptation he wrote was sufficient for scratching his rewriting itch, and no longer has plans to rewrite the book itself. The rewritten chapter fifteen he previously referred to remains unpublished though, and the audioplay doesn't even reach that point of the story.
From the Afterword of "Ender In Exile":
Therefore, I have rewritten chapter 15 of Enders Game, and at some future date there will be an edition of the novel that includes the revised chapter. Meanwhile, the entire text is online for anyone who has ever bought or ever buys any issue of my magazine Orson Scott Card's InterGalactic Medicine Show (oscIGMS.com). I have linked it to that magazine because every issue of it contains a story from the Enders Game universe. My hope is that if you buy an issue in order to read that revised chapter, you'll also sample all the stories in that issue and find out what an excellent group of writers we've been publishing there.