The 36112187043 spare has been mentioned before on this thread:
Spare Tire Comments
It is the correct size for the F25 at 27.7 inches in diameter, having a 135/80R18 tire instead of the 135/90R17 (27.3 inch) tire used on the E83. Haven't seen a MSRP in the US, or any US availability, but have seen it listed in Europe at 220 Euros.