1. BMW Performance knob will work but you'll need to cut your current boot (OEM knob and boot are in one piece).
http://www.getbmwparts.com/partlocat...catalogid=4462
2. many people who have issue with it's lightweight and long goose neck shifter, replace their oem goose neck to weighted ZHP knob. It's most popular option. And it matches nicely with rest of interior. But again, you'll need to cut your boot to re-use.
http://www.getbmwparts.com/partlocat...catalogid=4462