Those two take a Honda S2000 engine start button, but from what I've read, you can buy the OEM BMW button and I imagine it wires nearly the same way. Good luck, and for future reference, check out the DIY section first before you post, I found those in about 30 seconds. Good luck and let us know how it goes!
Oh and I believe both of those threads have links/info on where to purchase the button, along with how to install. If not, try RealOEM, they have everything.
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