If you don't get any luck with a second hand one, then get one from
here (which is where I got mine a couple of years back).
At current exchange rates you can get a brand new one for �285 as opposed to the extortionate �409 that TT UK are asking. TT Germany sell them cheaper than their UK shop but unsurprisingly won't ship to the UK! Nearly all the used ones I've seen on ebay seem to sell for more than the cost of a new one from the Motorcycle Luggage Shop?