Looking for a replacement shift knob for my 2006 Mini
 

The silver part on the shift knob on my automatic-transmission 2006 Mini has greatly worn away. It's purely cosmetic, but I'm thinking about replacing it soon. I'm just curious what kinds of shift knobs are compatible. I have no problem just buying an original OEM replacement, but if I could perhaps score a deal on something compatible, I wouldn't turn it down. Specifically, I was wondering if other BMW shift knobs are interchangeable with Minis, or if second-generation Mini shift knobs are compatible with first-gen Minis. Similarly, I've seen a lot of "universal" automatic shift knobs that don't have the trigger on them. How would this work? Would the shifter be in a permanent free-shifting state?

If nothing else works, I will happily just buy the OEM Mini shift knob. Just want to learn what my options are :)