I fancied a topbox rack for a while but hadn't seen one I liked (and thought the Givi ones were overpriced) then came across this in my local scooter shop, Beedspeed Grimsby, they're massive mail order sellers to those in Parkers and Fred Perry shirts.
It's a copy of the ones Triumph used to fit to petrol tanks, the one I bought is the lightweight version (there's another available with bigger tubing). For £30, and they threw in a free cargo net :-) I'm well pleased.