Just purchased 45litre black Honda topbox from David Silver UK.
See
http://www.davidsilverspares.co.uk/parts/by-part-number/partnumber_9182/ Colour code matches my new black ST1300 (compliance plate 6/11)
Service was excellent and delivery from UK to Adelaide took 10 days. Price was 295pounds plus 118pounds shipping!!! All up $651 by the time the credit card mob had applied its miserable exchange rate. Still cheaper than local version I believe.
Minor problems with collars supplied for mounting plate screws (may be my lack of technical competence!) so not sure if this was to suit earlier model. The UK site says it only supplies parts up to 2003 Pan European. The US site states that it supplies parts for up to 2010 Pan European. The same topbox was available there but David Silver US advised me it would be cheaper to buy from their UK site as freight was less!
Anyway, mounted it OK and it looks really nice. Can fit two full-face helmets easily:- Shoei XR 1000 (M) and Arai Vector (L)
Only been on short ride so far, but Cherrie says the back-rest is helpful although she has to sit a bit further forward on the pillion seat.