^^the only problem I see with using the above steel wheel (page one of this thread!) is that you have to NOT loose that plastic adpator PLUS you need different wheel bolts bc of the steel wheel. The bolt heads taper in a different fashion. The above steel wheel is from a X5. I am still kind of surpised this wheel clears the larger M3(&1M) brakes.
I don't think you can buy the complete spare wheel and tire like I did over here in DE. But you should be able to buy the alloy wheel and then source a mini donut from TireRack or the like.
Here is the alloy wheel for the M3 listed by RealOEM.com
http://www.realoem.com/bmw/showparts...74&hg=36&fg=95
Here are some pics of my spare tire setup on my 135i(same alloy wheel!)...
jack kit and tools = 71106773536 - 100 euros
alloy wheel/tire spare = 36110445045 - 120 euros
The original spare tire thread...
http://www.1addicts.com/forums/showt...ht=36110445045
Dackel