the wind deflector did come in a leatherette zipped handled bag, i have not seen any others so as far as authencity i took it on face value, have looked over bag and deflector for any part no etc, all i can tell you that it has three picture instructions on the bag with the vw logo in the top left of the first pic. it does appear to be well made (no tatty edges etc) but even at the price of £170 i think it is very very expensive for what it is, but hey its an accessory for my new arrival!!
the suitcase you missed, was it recent if so was it the one that had to be collected from york??? it was not me who won it, but thought someone had bagged themselves a real betty bargain there.
hope this has helped
have just looked on ebay at the sellers feedback score 258 with 100% , that may help you a bit more with your decision