You might be able to get one from SEAT Sport or maybe one of the teams who might have an old one lying around.

But they go right through the middle of the back window, so I don't really think you'll be fitting one.
 
yes you can get them from seat sport, but you will need the sub frame to go with
which will be a lot of work and i believe it would get in the way of the rear wiper motor. best of to buy a after market one
 
very true i would in that case ring seat sport and speak to darren in the parts department he will help