I have the same spare "kit" as pieced together here with the Maxxis tire.
http://f10.5post.com/forums/showthre...ighlight=spare
From the looks of the Bimmerzone ad, it also includes a centering ring, so it may be the exact same setup. Cover it and strap it down.
I also keep a ContiComfortKit in the trunk as a back up. It fits nicely in the passenger side trunk compartment.
You can get those from TireRack
http://www.tirerack.com/accessories/detail.jsp?ID=38