The 2008 x5 Sport Package came out with run flats and no spare. Some of the other model did come out with spare tires, and that is where I've sourced my.
The x5M does not come with spare and does not come with run flats.

Worst case scenario. You get a flat and need to get towed. In most cases it's still less then a set of run flats.

When you are buying the truck from a dealer, sometimes you can get them to move the spare from another truck (just to makes a sale).