I tried motorworks a few weeks back and they didn't have any.
Since my bike is a bitsa and has an R65 tank I was wondering whether the R65 toolbox would fit. Failing that I was going to buy some thin sheet ally and some alloy brazing rods from eBay and custom make one.
FYI The plastic these tool boxes are made of can easily have their shape altered with the heat of a hot air gun. So if you have one that's not quite right...............