i tried getting one the other week for my sedi, i was told fiat italy has stopped producing them, (dont know how factionally accurate this info is however) if this is the case your options are second hand replacement or recon, i was quoted around £80 for my drive shaft to be recon'd
I have 2 near as new damn it sedici drive shafts only did 2 races still have the stickers on them. £100 quid the pair if you want them - oh postage will be a fair bit as they are heavy.