Did you by the car new? If so they owe you money....

 

The bmw.de site is usually the best source for options information for EU spec cars.
Ski bag is part of the split/fold backseat option: "Durchladesystem, inkl. Skisack".
Option code 465.

I also checked the realoem.com parts diagrams. Only the folding seat has the ski bag,
whereas the non-folding seat has just a solid piece of plastic cover instead.

 

I took a look at the BMWUSA site and the 2007 order sheet and it looks like the ski bag is only available with the fold-down rear seats. It also looks as if the ski bag has nothing to do with the cold weather package...

 

Let's wake this up.
Ok, Skisack is not possible if You don't have Durchladesystem (folding rear seats).
But has anybony tried to make one?
Ok, the bag itself is simple. just make an order from BMW ,but how about the rest?
It looks like the central armrest is thinner in those durch-models, but this is not technical problem either = just order one, but!
This part is very expencive one, minumum 430 euros = too much.