I don't know how to get one of the buttons, but I remember that in the first few pages of this knit-along, they posted pics of the buttons that you can use. Maybe they talk about how to get it in your signature there.
Your dark mark scarf is looking great, rachejm! Also, your gryffindor scarf looks really good too!
gargoylelib, I really like the Charmed Knits book. It has a lot of cute Harry Potter stuff in it. Some of these patterns are already free on the internet as well, though not all of them are. I'm glad to have it though. I'm such an HP nut, I collect any and all the patterns I can just for fun!