After much searching I found a source that had a 2005 Chevy cobalt 15x4 space saver spare. Searches on the forum say that these fit the mini perfectly. I remember seeing a thread of someone posting pics of their mini with a cobalt spare on the rear.

Anyways you can find them here www.harryandsons.com for $35 plus shipping. To my door it was $50. The spare and the tire are absolutely brand new. Much better than $150 to get a mini original.

K

 

Have you tried it on the car yet? What is the hub size?

 

A honda Civic's tire will fit too.